I employed inexpensive C/D quality structural plywood for my son's DIY climbing wall, since the surface area could be textured with sand and painted. There were knots and holes in the outer levels, but on a climbing wall, People are features! This wood comes from trees on the Shorea genus, https://cumpara-online32975.blogdosaga.com/23805377/a-simple-key-for-plywood-unveiled