allen
adj. B2 Upper Intermediate US //ˈæɫən// allen
adj. describing a tool or screw with a six-sided hole in the top. You use these when you need to put together furniture or fix a bicycle.
adj. relating to or denoting a hexagonal socket-head screw or the corresponding wrench used to turn it. Frequently used as a modifier in compound nouns like 'Allen key' or 'Allen bolt'.
I need an Allen key to tighten the chair legs.
Most flat-pack furniture kits include a small Allen wrench so you can assemble the pieces at home.
The technician used a set of Allen bolts to secure the internal components, ensuring that the casing remained flush and free of protruding screw heads.
Usage
Commonly functions as an attributive adjective modifying 'key', 'wrench', or 'bolt'.