Unplasticized polyvinyl chloride (UPVC) is a low-maintenance material common in the U.S., UK and Ireland that is often used as a substitute for painted wood. It quickly became a favoured material for making residential doors due to its durability and affordability. Consequently, manufacturers were obligated to create said doors with a variety of different locks to accommodate households that wished to replace their old doors with new UPVC ones. The result was a wide variety of locks being made available on UPVC doors.
Deadbolt locks, also called deadlocks, provide a greater level of safety than spring-loaded locks since they cannot be pried open. The lock works by pushing a solid steel latch, often an inch long, from the edge of the door into the catch on the doorjamb. Deadbolt locks come in two major styles: single cylinder and double cylinder. Single cylinder means a key is required for entry from the outside but not from the inside, while a double cylinder, which is generally more secure, requires the use of a key from both sides.
A hook-lock throws a hooking bolt or multiple hooking bolts into a keep when the door is locked. A hooking bolt resembles the top part of a question mark and is typically made from hardened stainless steel or an aluminium alloy. These locks are most suitable for main entryway doors that do not require any sort of access or exit control. The door remains unlocked if the hook lock is placed in the open position while a simple thumb turn is required to operate the lock from the inside.
Center latches, also known as over-centre latches, are comprised of a base plate, a pivotally-mounted lever and a claw that is pivotally mounted to the lever. When in use, the claw operably engages the catch plate on the doorjamb to close the latch while a safety catch prevents opening of the latch when the catch member is in the engaged position.
Roller cam locks provide very little security compared to hook locks and deadbolts because the latch is only connected with a simple strike plate, allowing the locks to be pried open easily from the outside. When a key is turned, the cam uses a rolling mechanism to slide into and out of the catch plate. An alternative is a mushroom roller cam, which is similar to a regular roller cam except that the head of the cam is shaped more like a mushroom, giving it added latching strength.
Combination locks are one of the more technologically advanced types of locks used on UPVC doors today. On the front of each lock is a panel with a numbered keypad similar to a telephone. Most of these locks secure the door through a magnetic mechanism, and the correct combination must be entered on the keypad to gain entry. These locks provide some advantages to key locks in that there is no key to lose and no lock to pick. Although these locks are more common on commercial buildings, they have also gained ground over time in the residential market.