I utilised inexpensive C/D quality structural plywood for my son's DIY climbing wall, since the floor would be textured with sand and painted. There have been knots and holes inside the outer levels, but over a climbing wall, All those are capabilities! Plywood can each be sanded and polished. Like https://josueldrhy.blogocial.com/a-simple-key-for-plywood-unveiled-59517448