Like most over-toilet storage units, the back bracing piece could not be attached to the side pieces through the existing holes because the back of the toilet was in the way. We had to drill holes higher up on the side pieces. That's harder than it sounds--it's really hard to drill a straight hole of the right side through particle board. You need proper equipment, not just a drill. We messed up one piece, and the manufacturer sent us another. I wish these units all came with multiple pre-drilled holes on each of the side pieces, so you can attach the back brace wherever you can. Otherwise, though, it's a nice piece, good quality.