Key
A key was a small object used to open some kinds of locks.

On Earth, prior to the development of voice command activation, keys were used to start vehicles such as the 1936 Ford truck that  found floating in open space in 2371. ()

The Akaali used keys for their doors on their homeworld. Following a fight with an undercover Malurian, Jonathan Archer took his key to Garos' curio shop. ()

A key was used to secure handcuffs around Captain Jonathan Archer's wrists when the Ferengi were holding him prisoner. After rendering one of the Ferengi named Krem unconscious with a Vulcan nerve pinch, Sub-Commander T'Pol stole the key from him. She later teased Archer with the key, but eventually used it to unfasten the handcuffs. ()

In 2372 of the mirror universe, a Klingon guard accused  of stealing the key to his collar, an action Garak patently denied. After Regent  stabbed him in the abdomen, the guard realized that the missing key had fallen into his boot, instead. ()

See also 
 Code key
 Keys to the city

External link 
 
Security technology