Basic Hold and Volume Attachment – Theory and Tools

There are two main ways climbing holds are attached to the walls at the Spot–bolts and screws.  At The Spot Boulder the walls are concrete so most holds are attached with bolts only, and to tighten the bolts we use hand held t-wrenches. For bolts at The Spot Denver and to strip holds and put in screws at both locations we use an impact driver.  Bolted-on holds must be bolted into a t-nut.  Screwed-in holds must screw in to some stable surface, which is usually wood.   Wooden volumes are big features that are screwed onto the wall (in Boulder because of the concrete we first bolt wood frames onto the walls and we screw the volumes into those).  Holds can then be bolted or screwed onto the wooden volumes.  Below, I will explain what each of these components is and how we use them in day-to-day setting situations.




Most climbing holds are designed to be attached to the wall with a single point, which is a thick bolt.  The bolts we use are actually technically called socket head cap screws, because of their special heads that are tightened with an allen wrench and designed to be recessed into the item they are tightening.  There are two types of socket cap screws we use–square heads and martinis.


Square Head

Square head, aka socket head cap screw, aka socket head, aka standard, aka normal setting bolt. Notice the space between the head and the threads. That is 1 space, so we (at The Spot) call this a #2. A #1 has no space between the head and threads. A Zero is a 1/2 length #1. A #3 has 2 spaces. Etc…

The square heads are the normal bolts you see us using most of the time.  They take a 5/16″ allen wrench or 5/16″ hex bit to tighten, and once they engage the t-nut that is mounted into the wall, they suck down on a washer that is built into the hold and make the hold sit tight to the wall.

Imagine a washer built into the hold where the bottom of the bolt head sits. That allows you to tighten the hold to the wall without the bolt digging into the urethane/resin.  In Spot speak this is a #1 size bolt. Picture shamelessly stolen from

Many old climbing holds did not have a recessed washer, meaning that the washer was mounted on the outside of the hold and the head of the bolt stuck out once the hold was tightened to the wall.  This looked bad and proved to be impractical, as the bolt head could provide an additional place to stand or grab (as in thumb-catch) or the bolt head could be in the way of the proper grip position and could have caused injury or discomfort.  Luckily, someone figured it out, and recessed washers are now an industry standard.  Of course, there is a second option:



Flat head socket cap screw i.e. martini bolt.  This one is Spot size zero.

We call ’em martinis because their heads look like the tops of little martini glasses, but they are technically called flat head or countersunk.  Martinis recess themselves, so there doesn’t need to be a washer or a recessed washer, but for a martini to work properly the hold must be carved in such a way that the martini will sit flush to the hold’s material when it is tightened down.  This gives good surface area and prevents slippage or spinning.  The head of a martini is a bit wider than a squarehead, so on top of the obvious hole design difference it’s pretty easy to tell which kind of bolt you should be using because a martini won’t fit well in most recessed washer holds, and even if you do fit one in only the bottom of the bolt will be touching the washer, meaning there will only be a little surface area and the system will not be as strong as it should be.

Kind of like the drawing on the right, but if you imagine a hold instead of a piece of wood.

The martini is a good option for little holds (especially smeary or slopey feet) where a regular square head bolt would be impractical, either because it would be way bigger than the actual hold and thus be impossible to fully recess and therefore provide a bigger foothold than the hold you are bolting on to the wall, or because tightening certain tiny feet with a square head could break them (because there isn’t enough material in the hold to support the force of the tightening).  Martinis spread the force around a little more, and seem to take less force to tighten, so they work well in small hold situations.  Sometimes, however, a small-hold manufacturer has stuck a washer on the outside of the hold (or barely recessed it), so a martini is not the right bolt but a square head would stick out a lot and therefore not be the right bolt either.  In these (thankfully rare) situations, a third kind of bolt, the button head, can be used.


Button Head

A martini and a button head.  Both are Spot size 1.

Button heads are nice because they are fairly flat and smooth, so even if they stick out of the hold they do not provide an additional standing-on surface.  In general, they are the best choice for little washered holds because they look cleaner, stay out of the way, and tighten down properly on a washer. Small 7/32″ wrench needed for button head and martini bolts.


Red Handled T-Wrenches


The other benefit of the button head is that they use the same size allen wrench as a martini.  The wrenches we use are pictured below, with the big wrench being 5/16″ and the 2nd (small) wrench 7/32″.  Having to use two different sizes is not ideal, but two wrenches are still better than needing an entire wrench set.  Generally at the Spot we set with the big wrench, only using the small wrench and martinis and button heads when absolutely necessary for certain small crimps or no shadow feet.

Standard sized set of setter’s t-wrenches – 5/16″ and 7/32″.

These red t-handled are our favorite wrenches, because they are the most comfortable on the hand and have a little flex in the handle that seems to make the work easier on your body.  Also you can use one wrench in the handle of the other to increase leverage if you have a particularly stubborn hold, though since we set bouldering and therefore are always near the ground, we usually just get out the breaker bar.  More on that in the upcoming Stuck Holds article. For a while these red wrenches were hard to get, but fortunately many climbing companies now make it a point to carry these or other decent setting hand wrenches.


Other Tools


Other setters I have met have various opinions about which tools are the best, from ratchets to solid-handled t-wrenches to impact drivers, like the beautiful Makita in the picture below.  At the Spot Boulder we do not set with impact drivers, or even ratchets.  We hand-tighten everything.  At The Spot Denver the walls are newer and flatter so we do set with impact drivers, and for the most part they do make things go faster.

Our trusty Makita Lithium Ion Impact Driver.  You can probably get a set with the drill as well for a great deal on Amazon.

When we strip (i.e. take holds off the wall) we also use an impact driver.  The bit is a hexagonal (i.e. allen) bit that looks just like the head of the wrench.  It used to be, you had to buy a hexagonal socket set or make your own bits, but now climbing companies have these wonderful little quick-chuck compatible allen bits for the impact driver, and we use them most of the time.


These and other basic setting tools and hardware on

If you have a particularly deep-set bolt hole, you’ll have to either get a hand wrench, get lucky and find a long one somewhere, or make your own long allen bit by cutting a wrench and JB Welding it into a socket adaptor like I did back in the day.

A long allen wrench socket set. You’ll need a square head adaptor to use them with your drill.

The short set.  You can use these as well, with the square adaptor, and they work fine for most bolts except deep ones.  They’re not as good as the single piece bits, because with the adaptor they’re a little long and a little wobbly.  They’re good enough though.  You may have to tape/glue them onto their adaptors or they’ll pull off sometimes and either stay in the bolt or fall to the floor.  It gets annoying after a while.  So, not ideal, but passable.

Recently some other setters I know have started using a smaller, lighter version of the impact driver, but I don’t really like them because they are noisy and without the bigger battery on the bottom they don’t balance as well in my hand as the big Makita does.  On the other hand, a light tool can be good for setting on a rope, or for long setting sessions.  The drill/driver set looks like this:



The crucial accessories to have for a setting drill are:

1) Allen bits in both sizes

Single small bit.

The best big bits. Many climbing hold companies sell these now and some even have longer versions as well.


2) Several screw bits (we use Phillips and Star)

Phillips. Infinitely handy.  Right side is quick-chuck adapted.

Star (or Torx). It’s best to choose one or the other, cause if you keep having to switch back and forth with screws and screw bits, things get annoying quick.


3) A quick-chuck masonry drill bit (aka hexagonal drill bit) is useful for drilling guide holes in resin holds and heavily textured walls.  Drilling guide holes in urethane holds isn’t a bad idea either, cause it’ll get the extra material out of the way and keep the hole from getting gunked up when you put the screw in.  Also, some urethane is more brittle than it probably should be, and self-tapping a screw into it with no guide hole can lead to resin-like cracking of the hold or it’s edge.

One of the smaller sizes shown here is usually appropriate.




Screws can be used to attach holds to wooden walls, volumes, and other holds.  A screw or two can also be put in to a hold that is bolted on the wall as a “set screw”, or two can be screwed in near the hold as a “bracket”.  Self-tapping (aka self-drilling) screws are great, because you don’t have to have a guide hole, and even if a guide hole already exists in the hold, the self-tapper will get into the wall or wood volume nicely.

self tapping countersunk screw

When pressed we use decking screws or whatever else is handy, as long as the head is countersunk so the screw sits down in the hold and can’t harm the climber.  Make sure your screw is long enough that it gets several threads in the supportive part of the wall (i.e. through the concrete and into the wood).  Otherwise it might pull out of the wall and make an unsightly hole or crack in your concrete/texture layer.

If you have heavily-textured or molded walls (Monolithic, some Eldo), excessive screwing is a great way to ruin them. If you absolutely have to use a screw, drill a guide hole first and make sure you hit wood and use a long screw to minimize wall damage.  If you have a fiberglass wall (Walltopia), and you have to use a screw, it is best to screw in a horizontal line with the bolt holes as there are wood strips behind the bolt hole lines but the rest of the wall is just thick fiberglass–not as strong for screws and screwing into them is more likely to weaken or put holes in the wall.


Set Screws

Set screws go through the hold and into the wall.  They are used to keep holds from spinning, and are usually very effective.  Some companies pre-drill set screw holes with the martini shape in the resin so the set screw will not stick out of the hold at all when it is tightened and there will be no risk of injury from it.  If you have to drill the guide hole yourself, you can spin the drill bit around in the entrance of the hold a little bit and widen it so the screw will recess properly.  Even a small set screw should be enough to prevent a hold from spinning, except perhaps in cases where the hold is subject to a lot of violent torque, for example a hold that is dynoed to from the side or dropped down on from above.  Screws are weakest when twisted, so it is possible to break a screw in these instances if there is a lot of force put on them.  If you are setting a dyno or drop-down situation, it might be better to bracket the hold instead of screwing directly into it.  Here are some examples from the 2009 Mammut Bouldering Championship qualifiers at The Front in SLC, Utah.  The Front is all wood, so screws can go in wherever you want to put them and they won’t really harm the wall.

On a volume.  You can see a set screw in the top of the orange pinch. The climber’s shoe is on a screw on foot, also called a jib.

The T-Rex (peach hold) has several screws in it to make sure it is secure for all the yarding that will be done on it. The back screws might also be helping hold it flush to the wall so there is no edge for competitors to grab.  The red foot is a screw-on foot, and you can see 2 of the 3-4 screws that are holding it on the wall.



Bracketing a hold with screws means screwing two screws on opposite sides of the hold in such a way that the hold will be unable to spin in either direction after it is bracketed.  This can be done on a small scale, with a couple of screws under a foothold, or on a large scale, as pictured below. At a Junior Nationals in 2007ish, we set screwed or bracketed every single hold in every round.  In the case of a mostly-footholds route that one of the setters set, we had to bracket each hold by screwing two screws underneath it on either side of the bolt hole.  This made a kind of screw platform for the hold to sit on, and kept it from spinning.  You can also bracket with bolts or other holds, as seen here:

A Big DRCC Hold that is blocked because we couldn’t get it to fit on the wall with both bolts. The top block, a bolt, keeps it from spinning up, and the bottom block, the blue foothold, keeps it from spinning down.



This term generally refers to screw on holds with no option to bolt on.  We usually only use it in reference to small screw-on holds, and refer to bigger screw-ons simply as “screw-ons”.  Because many of the walls at The Spot Boulder are molded concrete over foam, putting screws into them could seriously damage them and also is not 100% secure because there is nothing of substance behind the concrete for the screw to screw into.  The Dojo can be screwed into (though we try to avoid it) and so can parts of the river wall and a small section of the Hueco.  The Beach is fiberglass, so it will accept screws but it’s better not to use them unless they are going in near enough to the bolt that they will suck into the wood backing that is in line with all the bolts, as mentioned above.

A DRCC foot jib screwed onto the edge of the volume where there are no bolts.

We use jibs to add-on to volumes or other larger holds. Often a well-placed jib will make an impossible pinch suddenly possible, or help you stand on the slopey top of an undercling. Jibs are especially useful as thumb catches. Jibs are the main reason we use screws at The Spot.

A DRCC jib used as a thumb catch at the Battle in the Bubble. You might notice the hold is cracked–the setter did not pre-drill for the screws for the jib and the hold cracked when the jib was being tightened onto it.




We have many volumes at the Spot.  We generally use the term “volume” to refer to the large wooden features (ours are all triangles) that stick out from the wall and temporarily change its shape. Other holds are then put onto the volume to create the route. Technically, volumes can be any shape and can be made out of a variety of substances, but usually are wood and/or fiberglass. Sometimes if they are wood we put grip tape on them to create a sticky spot to grab. In recent years, World Cup Bouldering events have been rife with volumes, with some entire problems consisting of volume wrestling.

Kilian Fischhuber dealing with the massive volume from Motivation Volumes on Men’s Final 4 at the 2010 Vail World Cup

Most World Cups are held on wooden walls, allowing 100% hold-placement creativity as any bolt-on hold can quickly be turned into a screw-on if so desired, and, as wood walls are generally flat, volumes can go anywhere. At The Spot our unique terrain means our volume placement is somewhat limited by where they will fit between curves and where we can fit a frame on the wall to screw the volume onto. The same problems as I mentioned above with screws in textured or fiberglass walls all apply here. At the Spot Boulder, we have a unique solution to the screw problem.

Matty Hong trying the hard beta on the volume problem – O10 at Highlines Highballs 2011


Adding a Traditional Wood Volume at The Spot Boulder

1. Setters decide where they’d optimistically like the volume to go on.

2. One setter holds the weight of the volume up against the wall while the other makes slight placement adjustments to make it fit best with the wall curves and bolt holes. Other setters often stand back and make commentary and suggestions. (Tip – you can bolt a jug or two to the volume to make it easier to lift and hold during this process.)

3. Once the placement is approximate the adjuster uses pieces of tape to mark the corners and sides of the volume. When the volume is taken away from the wall, a rough tape outline remains.

4. Wood or the pre-made wooden frame is fitted into bolt holes inside but close to the tape outline. Often this requires shifting the whole outline a bit to one side or the other and re-drilling the frame wood.

5. Once the frame is bolted on the volume is held up to it by one setter. If the volume fits over the frame a second setter begins screwing through the volume into the wood frame.

6. Many screws are put in until the volume’s sides are all sucked pretty close to the wall and the volume feels stable.

7. The edges are taped with 2″ black tape and the corners are cut with an Exacto knife so they are clean and match the lines of the volume.

8. The volume is ready to be set!

Many volumes for the French World Cup Team Selection 2011.


Bolt-On Volumes

The exception to the frame method is the bolt-on volume, which, as you might imagine, can attached to the wall with a bolt. These volumes are limited in size as you can only go so big with a single attachment point, but we have a few triangles that you may have seen around. They are definitely handy and much easier to get on and off than the traditional wood volume.

The DRCC Bolt-On Volume is handy because there are so many bolt holes in it!

Motavation Volumes Bolt-On – We have a few sizes of this model. Click the photo for their site.

There are many other kinds of amazing volumes including wood, fiberglass, plastic, and…other…materials that have shown up in recent years, including walls with built-in volumes and walls consisting purely of hanging volumes. Stay tuned for more on volumes, as well as articles on bracketing, comps, stuck holds, and other setting tips, tricks, and techniques.

  1. March 4, 2013 at 6:35 am

    Good page. Thanks for the info.

  2. Kevin
    December 13, 2018 at 1:43 pm

    Do you ever adapt a bolt hole in a bolt-on hold to take a screw? What do you use in that instance?

    • Jackie
      December 17, 2018 at 1:40 pm

      Yes you can use a bolt hole plug that takes a screw in the screw hole. Kilter sells some plastic ones in colors that match Aragon holds, and some other companies sell metal ones (like Fat Cap and Escape has one called the Lone Star).

  1. January 5, 2012 at 5:42 pm
  2. February 22, 2012 at 4:12 pm

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