First, assess the open space in your garage or basement: Ideally, you want to use a wall that’s at least eight feet wide, in a room with a 10-foot ceiling. Those dimensions will give you a 12-foot climbing surface that overhangs 40 degrees. (While vertical walls are easier to build, overhanging ones are more fun and yield better training results.)
This setup also lets you use three full sheets of plywood — if your ceiling is shorter, you’ll have to cut the boards. Then build a frame by positioning two-by-six studs every 16 inches, anchored at the floor and ceiling to support the plywood. Use 3/8-inch T-nuts set into the back of the plywood to anchor your holds. (The holds from soillholds.com are strong and light, and starter kits are available.) Design a pattern that won’t interfere with your frame, drilling a grid of holes using a 7/16-inch bit — the same diameter as the T-nut barrels’. Drill enough holes so that you can easily move your holds at a later time. Finally, screw the plywood onto the frame and set your routes.