Mine is 2 sheets of 3/4" plywood glued and screwed together and then glued and screwed to a frame of 2x4s and it is rock solid. I can jump up and down on it all day long and it wouldn't even flex. Downside is that the plywood is a relatively soft work surface. I'm considering coating mine with some sort of epoxy or polyurethane to protect the surface from dents and marks. If I had to do it again, I might consider getting a cheap countertop instead of all the work I put into the plywood bench. (I admit that the labor was part of the fun for me... I love building things, but the convenience of a prebuilt countertop is appealing.)