Selection of Holds, Bolts, and T Nuts
A good rule of thumb is to have at least 5 holds per square meter of wall surface. That means around 30 holds per full sheet of plywood.
Selecting holds depends a lot on the angle of your wall and your ability level, and what you will use it for.
If your building your 1st ever home wall , you can get by with 15 to 20 holds per sheet, but the more holds you have, the better your wall will be. Many home walls end up with over 100 holds per sheet of plywood.
There is a huge variety of specific hold shapes. Our friends at Uncarved Block are coming up with new moulds every week. For now though just make sure you have the right mix of hold types.
50-60% should be medium-sized bolton holds of mixed styles (edges, pockets, pinches, slopers, etc.).
20% of your selection should be footholds. These can be small bolt-on holds or even screw-ons. Screwons can be useful to put in places that bolts cant go, like right in the corners or over the frames.
10% of your selection should be small handholds. These will be very similar to the footholds, but slightly larger and more positive. (Just try to make sure that about 30% of your total selection consists of a good variety of small holds, as these are the ones, especially the small footholds that will make you better!).
10 to 20% of your selection should be jug holds, these are big holds that you can really get a good grip on, we have a good range ‘Kids jugs’ which are for smaller hands, but sized and priced like medium holds.
The T nuts most commonly used are coincidentally the cheapest ones, at around 15 cents each. They are of Zinc plated steel and 3/8 inch thread, these are great and attach easily to the back of the wall via their prongs, (it is worth spending some time to fit them flat, as this will help when you put the bolts in).
Stainless steel T nuts are considerably more expensive (and can be hard to get), but if your wall is outside, or in a very humid spot, Stainless T nuts are worth the investment. If you have ever tried to get a bolt out of a rusted T nut, you will appreciate stainless.
The problems arise after a few years when you want to move holds around or remove them. The T nuts are on the back of the wall are usually difficult or impossible to access.
If the bolt is seized into the T nut, OK leave it on, but if it is spinning and need tightning if you can access a rusted T nut and are trying to remove the hold it is securing you are likely to make a bit of a mess with chisels/ grinders/ hammers.
Most climbing holds attach with 3/8″ socket head cap screws. There are 3 different types of heads that are commonly used. Each different style works with a different shape of hold. The most common style is the standard socket head. This is the strongest.
Different holds require different bolt lengths. you must use the correct length bolt for your safety. if you are putting holds onto 17mm thick plywood the bolt should poke out the back of the hold at least 20mm to fully engage the T-nut threads. It is okay to use a longer bolt but make sure that there is space behind the wall to receive it, and that the unthreaded part of shoulder of the bolt isn’t so long that you cannot tighten the hold properly.
Because most T nuts are 3/8 inch thread, you will need UNC threaded bolts, this is bolt language for an Imperial ‘Coarse Thread’. UNF defines a ‘Fine Thread’ and will not wind into your T nuts.
If your wall is inside rust will be much less of a problem, phew. you can use standard zinc plated or even Black bolts.
If your wall is to be outside, and particularly if it is exposed to salty air, then you may consider using the more expensive stainless steel bolts.