wood - Boards provide support by forcing the proper amount of knee (or arm) flexion.  The boards can be used on a treatment or mat table or on the floor.  Can support progressive resistance weight exercises.  Board folds flat when not in use.  Available with or without vinyl covered foam padding.  steel - Each section can be adjusted independently to match exact femoral and tibial lengths. The infinite adjustability of this quadboard allow for the knee to be fixed to any degree. Chrome plated steel, folds flat.