The wooden block is placed under the buttonhole to support the fabric; the chisel is pressed against the block from above. The chisel's knife is positioned in the centre between the beads of the buttonhole, and with only slight pressure, cuts through the fabric directly onto the wooden block.
Thanks to its precise design, the blade slices through the buttonhole cleanly and accurately, without damaging the buttonhole's beads and bartacks. This helps prevent unsightly fraying of buttonholes on garments.