Materials: Five white Billy Bookcases We was inspired by other Billy Hacks found here. We were in need of an understairs bookcase and we love the minimal and simple look (and affordability) of Billy so we tried to adapt them to my space. The basic tool we used is a circular saw. So we started from left mounting one module at at a time. All modules are of the regular Billy with the exception of the second one to the left cut to end where the floor step is. Apart from circular saw we have used hammer, ruler, Spirit level, wood screw, wood glue and wood plug. In the end our “best friend” was white Stucco which we used to fix all imperfection and holes.