This bundle includes the Hammer Filing Jig, which provides a flat, smooth surface from which to control the filing of upright or grand hammers with a drum sander, and the Squaring/Filing/Voicing Block, which serves as a hammer support (their tails stand on the SFV Block) approximately at strike for hand and gang filing when a Squaring Platform is unavailable. With a Hammer Square, it can also serve as the horizontal base to square hammers to vertical and as its name suggests, it can also support hammers for needle style voicing.