A Crocodile clip lead is a one metre length lead, which ends in a pair of crocodile clips.

When the crocodile clips are not connected the circuit is open (OFF). When they are connected the circuit will be closed (ON).

A Crocodile clip lead is normally used attached to a home-made or commercial switch. They can be used singly or in pairs to provide timing and event monitoring.
 

Lead with Crocodile Clips (pair).
For connecting 'home made' switches.