A slim jim (more technically known as a lockout tool) is a thin strip of metal (usually spring steel) roughly 60 centimetres (24 in) long and about 2–4 centimetres (0.79–1.57 in) wide originally marketed under that name by HPC Inc., a manufacturer and supplier of specialty locksmithing tools.
Slim jims are used to unlock automobile doors without use of a key or lock pick, and are commonly used in grand theft auto.
It acts directly on the levers and interconnecting rods that operate the door, completely avoiding the complexity of dealing with the lock mechanism itself.
The hooked end of the tool is slipped between a car's window and the rubber seal, catching the rods that connect to the lock mechanism.
However, according to research by the National Highway Traffic Safety Administration, this has not been verified and manufacturers state it is impossible.