What is a T-nut and how does it work? How do you fasten ‘Bolt-on’ climbing holds to wood climbing walls? This guide is intended to be a quick explanation for customers who are brand new to climbing or are building a climbing wall for the first time. Prior to fastening bolt-on climbing holds to wood climbing walls, t-nuts must be installed in the back of the climbing wall. The bolt will go through the climbing hold, through the wood, and into the t-nut. A t-nut is basically a nut with a flange on one side. If you need help installing t-nuts check out our instructions here: How to Install t-nuts Purchase T-nuts The barrel of the t-nut can fit into a 7/16” hole, but the flange is 1” wide so it cannot fit through the hole. The flange catches the surface of the climbing wall surrounding the 7/16” hole. Once installed, the barrel of the T-nut should be recessed behind the front surface of the climbing wall by at least 1/ 4”. Climbing holds must not make direct contact with the t-nut. If the climbing hold makes direct contact with the t-nut it will eliminate the friction between the surface of the climbing wall and the back of the climbing hold. This friction is what keeps the holds from spinning. Climbing holds must have good contact with the climbing wall in order to be secure. Let us know if you have any questions! Matching holds with the proper bolts: Every climbing hold has a different shape and structure. Because of these variations, the depth of the bolt hole varies from one climbing hold to another. Example: The 20 pack of Frogs Jugs to the right consists of several different shaped grips. To fasten thes grips to a 3/4" wall you'll need (3) 1 1/2” bolts, (13) 1 3/4” bolts, and (4) 2” bolts. (We normally send 25 bolts just so you've got some wiggle room.) Frogs 20 Pack The easiest way to select the proper length bolt for each hold is to: 1. Separate your bolts by size 2. Grab a handhold and a bolt you think might fit. 3. Grab a ruler and measure the length of bolt sticking out the backside of the handhold. 4. If you've got a 1 1/2” thick wall, the bolt will need to protrude out the back of the hold about 1 1/2 inches. 5. If the bolt is protruding more or less than 1 1/2 inches you can select a different bolt and use the one that ends up pro- truding the closest to 1 1/2 inches. (it doesn't have to be exact) 6. Using this method you'll be select the proper bolt for each handhold. The length of the bolt needed to fasten a climbing hold to a wall depends on two factors: 1. What is the thickness of the wall? 2. How thick is the part of the hold the bolt must pass through? Basically, the depth of the bolt hole in the climbing hold + the thickness of the climbing wall = the proper length bolt for this hold on this wall. Download the full pdf (printable version)