A tap is a type of bit tool that fits into a tapping machine or a T-wrench to cut the female threads into a hole so that a bolt can be screwed into it. Most are made of high speed steel and come in three main styles: a taper tap (the most common), a plug tap and a bottoming tap. Taps are listed as individual units, or in tap and die sets, or just as tap sets. Taps can vary by thread size, number of flutes, tap dimension unit-of-measure type (inch or metric), tap style (pipe tap, point tap, flute tap, etc.), tap chamfer, thread direction, material, and other considerations. Flute taps are taps that also have flutes to channel away debris and deliver coolant to the hole being drilled.