Allan B. Colombo
Let us take a look at what is commonly referred to as an auxiliary lock. An auxiliary lock is any lock installed on any exterior or interior door that offers additional security to the lock mechanism already installed there. Even dead bolt locks fit this description. However, it is common to find old timers referring to rim cylinder locks as auxiliary locks. Some also call rim cylinder locks spring latching locks. The technical name is rim night latches.
Let us take a quick look at the rim night latch lock in Figure 1. This lock automatically locks after a person goes through and closes the door. This particular lock also has a small thumb latch that allows the spring latch to remain in a retracted position, thus, allowing acces at any time.
Somewhere along the way the public decided they needed a lock that wouldn't easily give in to credit cards, putty knives, and files. This led the industry to modify the latch on the common rim night latch; the result was the deadlock night latch shown in Figure 2.
This lock has many of the features found in a dead bolt lock, foremost being the positive dead-latching feature.
The dead-latching feature is accoomplished in a variety of ways, depending on the manufacturer. The dead-latching of any mechanism is usually attained by a lever that secondarily locks the latch. Unless a key is properly used to retract the latch, this lever remains in place to assure its integrity. Yet, even though the deadlock night latch keeps most people out, the need for still a better locking mechanism led engineers to develop the rim deadlock, pictured in Figure 3.
The difference between the deadlock night latch and the rim deadlock lies in the latch itself. The dedlock night latch still allows the door to automatically lock when the door is closed. Its latch is spring operated so it will retract when the door closes, automatically extending itself into the strike.
The latch used in the rim deadlock is more like the dead bolt lock. Its latch must be retracted by hand when opening the door and relocked manually when the door is closed. It is not spring loaded, which means it depends entirely upon the person gonig through the door to relock it.
Although the improvements on the rim night latch that made the deadlock night latch a more secure lock improved the over all security of the home, it wasn't the total answer. The weak point of both of these rim locks was their inability to withstand extreme conditions of prying. A heavy crowbar applied would often result in locks and strikes both being ripped off the door!
This became such a problem that engineers decided modifications had to be made that would eliminate this problem. As a result the jimmy-proof lock was born.
Jimmy-proof locks come in many forms, but they all have one common thread: the latch locks into the strke, preventing the mechanism from easily separating from one another. The combined strength of both strike and lock body gives the door greater overall resistance to attack. Figure 4 shows us a Taylor jimmy-proof lock.
A rim lock, regardless whether it's a night latch, deadlatching night latch, a rim deadlock, or a jimmy-proof lock body, has the same underlying components connecting it with the outside surface of the door. Figure 5 shows the mechanism involved.
The cyinder and collar both rest on the outside surface of the door. On the inside the remaining plate holds it all together with the help of the mounting screws, which run through the retaining plate, through the door and into the cylinder. The tail piece connects to the main lock body through a slot in the back of the mechanism. When a key is inserted and turned, the tail piece turns the lock mechanism in the lock body, thus retracting the latch mechanism.
It's important to understand how the rim lock fits together to appreciate the importance of protecting the cylinder. Many burglars have found it easy to twist the cylinder in the door. By doing so the cylinder and tail piece can actually be removed, for once the mounting screws have been twisted and broken, there's nothing to prevent this from happening. The burglar then simply inserts a screwdriver into the slots in the lock body on the inside of the door and turns the mechanism open, just as if it were the tail piece doing the turning.
The remedy to this is the cylinder guard, shown in Figure 6. As you can see, a claw device or heavy pipe wrench can not easily compromise the cylinder when the guard is in plce. Let's take a look at how we install the outside cylinder, collar, retaining plate, mounting screrws and lock body.
Introduction to Auxiliary Locks
How to Install An Auxiliary Lock, Part 1
How to Install An Auxiliary Lock, Part 2
How To Install An Auxiliary Lock, Part 3, Two Tips Worth Noting
How to Install An Auxiliary Lock, Part 4, Final Word