The highly dangerous and historic practice of inserting a copper coin into a threaded fuse socket before screwing in a blown fuse. This restores power by bridging the contacts but completely removes the overcurrent protection, guaranteeing that the wire will melt or catch fire if the circuit overloads.
Some idiot pennied the main lighting circuit and nearly burned the whole shop down.
Finding a pennied fuse during a service call is an immediate red flag that the building's wiring has been severely abused.
Related terms
Fuse
A sacrificial safety device that melts to break an electrical circuit when too much current flows.
Fuse box
An older style of electrical distribution panel that relies on replaceable melting links for overcurrent protection.
Circuit breaker
An automatic, resettable switch that protects an electrical circuit from damage caused by excess current.