Final answer:
An Allen wrench or hex key wrench is an L-shaped hexagonal tool used to tighten or loosen machined setscrews.
Step-by-step explanation:
The wrench with an L-shaped hexagonal design that is used to tighten or loosen machined setscrews is called an Allen wrench or hex key wrench. It is a type of tool that fits into the socket of a screw or bolt head with a hexagonal shape. The L-shaped design allows for better leverage and torque application.