How a Trunk Lock Works in a Car

Trunk locks keep the trunk or tailgate of a car locked for protection. They differ very little from the locks of car doors and other common locks on vehicles. Most are divided into three different sections: the lock mechanism itself, the emergency trip-lock mechanisms and the automatic release mechanism.

For many years, the lock mechanism worked the same as key-oriented locks for car doors. The main components of these locks are the traditional cylinder and striker: the cylinder holds the tumblers and other mechanisms necessary to unlock the trunk, while the striker includes the latch that actually holds the trunk shut when locked. Most cars have both the cylinder and the striker located on the lid of the trunk, but this does not always hold true--there are many different trunk lock designs, and some may separate the cylinder and striker on different parts of the trunk. When doors moved to electronic and radio-activated locks that could be operated remotely, trunks were a few years behind. Now many trunks, especially on compact cars, are also opened remotely, and some may not even include a traditional cylinder.

Trunks that still use cylinders generally employ a six- to 10-tumbler mechanism. The more expensive or safety-conscious the car is, the more tumblers the trunk will have, although it is common for the trunk lock to match the door locks in terms of tumblers, so the same key can open both. Of course, there are also cars that come with trunk keys that can only open the trunk lock, and vice versa.

The emergency trip device is a simple mechanism located inside the trunk, usually in the form of a handle or lever. It opens the trunk from the inside even if the trunk is fully closed and in the locked position. This is a safety design so that anyone locked in the trunk can get out by finding the emergency handle. Some of these devices may be a separate lock that opens to the interior of the car instead.

The automatic release mechanism is a feature long included in cars that allows the driver to remotely open the trunk while inside the car, usually by pulling a lever. This activates a solenoid, which uses electromagnetic fields to move and operate devices--in this case, the trunk lock. Solenoids are also used in the key chain remote systems popular today. The in-car release mechanisms were originally created for efficiency, so that drivers could open trunks before getting out and accessing them, without wasting time using a key to open the lock.