Halder tommy screws—often searched as thumb screws or hand screws—plus knurled nuts are hand-operated fasteners designed for tool-free tightening and quick adjustments in fixtures, machine guards, jigs, and industrial assemblies (application dependent). These fasteners are commonly used when changeovers are frequent and you want a secure grip for tightening by hand without reaching for a wrench or driver. Depending on the style, tommy/thumb screws may provide extra leverage for hand tightening, while knurled nuts offer a compact, high-grip option for quick clamp-up (application dependent; verify per listing).