A thumb screw is a screw that is designed to be tightened and loosened by hand without the use of any tooling. The head of the thumb screw is knurled to provide extra grip and prevent slippage when tightening and loosening. The head diameter is large for ease of use and also provides a high degree of rotational accuracy. Types of Thumb Screws Thumb screws can be made from a range of materials including steel, brass, nylon and resin. A range of thread sizes and lengths are also available. Applications Thumb screws are ideal for use in machine and computer applications where there is restricted space and fastening tools cannot be used.