Screw having external driving recesses

摘要

A screw nail having a nail head with rounded peripheral portions alternatingly arranged with vertically cut external recesses. Gyration power for insertion or removal of the screw nail from a target surface is transmitted to the screw through the recesses using a suitable driving device. A groove in the flat upper surface of the nail head is of auxiliary use for transmitting rotational force, but is of insufficient depth to drive the screw nail into a surface independently of the recesses. By driving the screw nail using the external grooves, the requirement for alignment with the driving device is reduced and, because the nail heads can be thinner, the screw nails may be more inexpensively produced.