Things you'll need:
- Some 3/4" plywood
- Some 2x4s (or 2x6 or 2x8) for framing and such
- 2" (or so) wood/drywall screws
- 3/8" t-nuts
- 3/8" hex cap bolts
- Drill, hammer
- Something soft to work as a crash-pad
Step 1: Clean
Step 2: Framing
Step 3: Prepare and Install Plywood
Next, you must determine how many t-nuts you need. Generally, about 70 per sheet is a good guess. They can be placed in arbitrary patterns (diamond and square are common). However, placing them randomly and then eyeballing for uniformity works just great. When placing them, try to keep them around 8 inches apart and 4 inches from the edges or from any structural boards you'll be nail/screwing to. Since our wall was used as shelves there were lots of boards to avoid.
The t-nuts are 3/8" inner diameter and 7/16" outer diameter. This means you'll need 3/8" bolts and you'll want to drill 7/16" holes to pound them into. Hammering them in is pretty straight-forward.
Step 4: Hang the Wall
If you want a crack, build in vertical reinforcements using sections of 2x6 (or 2x8, 2x10, ...). These will have alot of force on them, so make sure they are very rigidly installed. For "hand" size jamming, 1 7/8" to 2" is just about right.
Step 5: Add holds, climb
More information on making holds here and here.
For a crash-pad, we used an unused mattress. If you have a crash-pad already, for bouldering, use that. You can probably make one of these too.