Excalibur Climbing Wall, Groningen, The Netherlands

Wall types
The simplest type of wall is of plywood construction, known colloquially in the climbing community as a 'woody', with a combination of either bolt-on holds or screw on holds. Bolt-on holds are fixed to a wall with iron bolts which are inserted through the hold, which will have specific bolt points, and then fixed into pre-allocated screw-threaded holes in the wall. Screw-on holds are, by contrast, usually much smaller, owing to the nature of their fixing. These holds are connected to the wall by screws which may be fastened anywhere on the wall's surface.
Other types of walls include slabs of granite, concrete sprayed on to a wire mesh, pre-made fiberglass panels, large trees, manufactured steel and aluminum panels, and textured fiberglass walls.