This doweling jig is pretty easy to use. Instructions are on back of box. It conveniently allows one to drill a pair of holes (in the same surface) for 3 common dowel sizes.I had a couple of problems with the unit I received. First, the clamping flanges (the outer shiny parts) are aluminum and easily bend (splay) outward when clamped. This allows the jig to rock slightly, so you must pay attention and keep everything aligned (or shim the bottom edges of the clamping flanges appropriately. Second, in the unit I received, the holes were not dead center between the two clamps. They were off sufficiently (as determined by calipering a drilled hole) that I had to shim clamping flange on the handle side of by more than 1/16".When you get your unit, drill some sample holes and check for centering.I'm not sure if I would order this jig again.