I have the part taken from the hardware store when I bought for the basement shelf rails. In order to fix them were to drill 12 holes in three rows which it arrived each at the same height. With the laser part that goes really easily by hand: position for the first hole set, then the laser beam directed on it and adjust based on the spirit level straight. Then along the beam scribing the other holes, drill, ready. The thing is not very cheap but very helpful.