This Mortising Chisel is great for drilling square holes in wood with a mortising machine or a mortising attachment. Reduce labor intensity of construction workers, speed up the construction speed, reduce construction costs for construction, installation, renovation, decoration industries. Square hole drill can not be used on an electric drill, drill square holes need to fit a square hole drill drilling (mortise and tenon machine) to use. Mortise and tenon square hole drilled by the terrible + outer sleeve in the middle of the combination.