Custom Drill Jig
The drill jig is designed to fit over dimensional lumber (2x) on end.
Simply drill your first hole put the male bushing into the hole that you just drilled and use the opposite end drill bushing to drill your next hole. Using the jig will give you 4-5/8″ on center for baluster installation and meets code for spacing. If your material is thinner than 2x or larger just bend the side ears in until you have a nice fit on the material your drilling.