Square mortising chisel Drill Bit 1. Hand drill with core drill 2. Adjust the depth and drill into shape 3. Pat lightly with the square diamond jacket. 4. Square hole forming. Suitable for Board, Medium Fiber, Particle Board, Density plate. 1. Sharp Edge 2. Strong and STurdy 3. A lot of Uses. a. Using the core on an electric drill to drill a round hole, then cut the square hole manually with the drill brush. It is very suitable for drilling square holes in wood with mortise machine or mortise accessories.