Most locks, even those referred to as "electronic", still require a manual device to engage and disengage the bolt. Electrically activated locks, however, provide added functionality by allowing remote activation. These are most commonly the "buzz-in" systems you see in use in apartment buildings and reception areas, but they can also be put on a timer to allow public access based on day and time. A common use for these is in laundromats and other places that are not staffed. The mechanical portion of these locks come in two general types — electrically activated latches, which control the latch, and electrically activated strikes, which control the strike plate. In the event of a power outage, these locks can be either "fail-safe", which default to an unlocked position, or "fail-secure", which default to a locked position.
Commercial keyless locks (also sometimes known as "cypher" locks) usually use combinations rather than keys. Low-end keyless locks are mechanical and typically hold just one combination, whereas high-end keyless locks are electronic, and are a form of access control. Combination locks are a simple solution for businesses that have high employee or tenant turnover and need to add or remove access frequently. Mechanical keyless locks have their own advantages such as not having to worry about power outages or batteries. In addition, combination locks have the added advantage of being without keys that can be lost or stolen, and combinations can be changed quickly. However, combinations can be "stolen" by watching careless users, so more caution is needed.
Securing double doors can be a challenge, as they often lock clumsily into each other instead of a stable frame. One way to compensate for this is by adding what is called a "mullion". This is a removable post that can be installed between the doors when locked. The doors then latch into it instead of each other which provides much more stability. We can also install a special lock that creates a "three point system" which, by throwing one lock, will bolt into the door frame at two points on the top and bottom as well as the adjacent door.