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
The first step is to choose a location. For us, the perfect location also was so cluttered with things, that you couldn't see the floor. So, for two days (and many beers) we cleaned. We carted away junk, created a pile of things to sell, and reorganized things that needed to be kept. In the process, we found many cool treasures.
Step 2: Framing
The wall you choose to build on needs to be framed well. It will need to support dynamic loads. Lucky for us, this wall, which was being used as shelves was built to be load-baring. A couple of nails here and there, and a a board along the bottom to complete the frame, and it was good enough to use.
Step 3: Prepare and Install Plywood
You will need to figure out how much plywood you need. The right plywood is 3/4" and the cheapest is just fine. We didn't have much luck locating used plywood, so we bought it new for $20 per sheet.
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
2" self-tapping wood or drywall screws work well for hanging the sheets. If you're having troubles, drill pilot holes.
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
You'll need to make or buy some holds. Store-bought resin holds cost about $4-$5 each. You can make your own a variety of ways. You can make resin holds using a mold (as is described in this instrucable), you can drill 3/8" holes in rocks (use a masonry bit, add water as you drill, some will break, some will work, don't bother with quartzy rocks), or get crafty with wood. Or, you can use just about any damn thing you can find and drill a 3/8" hole in (a drill-press is your friend).
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.