How Does a Plunger Lock Work?

Basic Lock Function

• Most locks, aside from deadbolt and combination locks, feature an internal cylinder that is manipulated by a key. A key that fits inside a cylinder will allow the cylinder to move a component called a cam, which either releases or shuts the bolt to open or close the lock.

Pin-and-Tumbler Lock

• Inside the cylinder of a pin-and-tumbler lock are pairs of pins, each pair a slightly different length than the others, and held in place with springs. When you insert a key, the “hills” and “valleys” of the key push the pins inside, up to set levels. When the pins are lifted to these levels, you can turn the key and manipulate the cam to release or shut the bolt.

Wafer-Tumbler Lock

• A wafer-tumbler lock works similarly to a pin-and-tumbler lock; however, instead of pairs of pins, there are thin “wafers,” or "tumblers" that are pushed into position with the key. Wafer-tumbler locks are less often used in plunger locks, which require higher security, as the keyholes are wider and the wafers easier to manipulate. These factors make wafer-tumbler locks easier to pick.

Locking Mechanism

• In a plunger lock, the cylinder itself contains a locking mechanism, a plunger, which, when depressed, pushing the cylinder flush against the outside of the lock, pushes a brass or nickel plunger through the back of the lock housing. This moves the cam in the same direction as when a key locks the lock, and engages the bolt to lock.