Is the process by witch threads are created in a hole. A tap looks like a cross between a drill bit and a screw. The size of the hole must match the size of the desired tap size. The correct hole size can be found on a chart or on the drill and tap holder in the Design Studio. In the example of the clock: the Upright comes with two 0.123" diameter holes towards the bottom. A 0.123" diameter holes is the size that is needed when you create threads using a 8-32 tap.