The base is a 5/4 frame surrounded by colonial baseboard. The frame has cross members at each end and splitting each seam where the cupboards meet. The 5/4 is 3.5" wide and the baseboard is 4.5". I sit the cupboards on the 5/4 frame and the lip of the baseboard and the weight of the piece keep it in place. You could always put one screw in through the bottom of the cupboard into the 5/4 at each end if you prefer. The weight does the trick though- I have these in houses where there are little kids so I wouldn't take chances. I made sure they were stable before doing it that way.