The blade of a three file combination rasp, unlike other dry wall rasps, is made of plastic. It has three different types of teeth designed into its blade, and can remove material on both forward and backward strokes of the tool.
Teeth
The coarse teeth are recessed from the others and allow you to remove large amounts from the edge of plasterboard quickly. The fine teeth remove less material than the coarse ones, but will give a better quality, smoother finish to the edge of the plasterboard, while the edge teeth are used to create neat, accurate corner edges on cut-out sections, such as around sockets and light switches.
Handle
The handle of a three-file combination rasp is also made of plastic. As the teeth cut away at the plasterboard, the shavings and dust are channelled to the underside of the handle where it exits slots at each end of the handle.
The handle is flatter and less raised than that of a pocket dry wall rasp, so even though the rasp is longer and wider it will still fit in most tool belt or pouch pockets.
Embedded grip
The handle has embedded grips on each side made of an elastomer that gives greater comfort and better grip when using the tool.