High Quality SteelThis square hole drill bits are made of special steel, heat treatment, hrc48-50, features high hardness, long core and high concentricity. Sharp blade, continuous, fast cuttings, high efficiency. How To Do The Work: The square drill into the hole drilled by the rotary body, while the impact of the use of force of percussion transmitted to the outer body, the grinding material round hole and square head wall, and the debris will be discharged from the tube at the same. Labor Saving and Precise: This Professional mortising chisel ideal for drilling square holes in wood with a mortiser or mortising attachment. And reduce the labor intensity of construction workers, speed up construction speed, reduce construction costs for construction, installation. 6 Different Sizes: 6 pieces at packaging with different slot diameter to meet your needs. Comes with 6 different size: 1/4" 5/16" 3/8" 1/2" 9/16" 5/8", suitable for opening different square holes. Application: Fits all mortising machines and drill attachments. Square hole drilling is mainly used for woodworking aspects. Professional tip, suitable for construction, design, renovation, decoration, etc. Please note: the chisel alone does not work in a wood drill, you need an attachment for your drill.