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Deadbolts and Auxiliary Deadlocks


There are three main types of deadbolts:

  • Tubular (or Cylindrical)
  • Rim (surface mount)
  • Mortise

This article discusses the installation details and relative merits of each, as well as what to look for in terms of quality and security.

Deadbolts are usually considered an auxiliary lock because, with the exception of aluminum and glass storefront doors, they are not the primary means of latching the door shut.

Tubular Deadbolts

Above is a the first page of the B600 Series section of the Schlage commercial price book, showing an exploded view of the B600 series deadbolt.  Notice the “Security Shield” that protects the bolt from attack through the door.

Tubular (or cylindrical) deadbolts are by far the most popular deadbolts used today.   Preferred by renovation contractors for their ease of installation, they differ greatly in quality and security.


Tubular (or cylindrical) deadbolts are generally installed into a modified 161 door prep – that is, the same prep that accepts a standard cylindrical doorknob or lever set.  The 161 prep consists of a 2-1/8 inch diameter hole drilled through the door.  This hole is called the “bore.”   A second hole, called the “cross bore,” is then drilled from the lock edge of the door to intersect with the bore.  This second hole is usually 7/8 or 1 inch in diameter and is located on the center line of the first hole.  See diagram:


Quality and Security

Quality in tubular deadbolts ranges from the relatively poor quality of inexpensive locks widely available in lumber yards and hardware stores to high security versions available mainly from locksmiths and other security hardware specialists.  The differences between cheap and good are:

  • Sturdiness of the bolt
  • Strike reinforcement
  • Guarding of the bolt
  • Sturdiness of the cylinder collar
  • Bump, pick and drill resistance

The bolt is the actual part that projects out of the door and into the door frame.   The sturdier it is, the harder it will be for a burglar to break it off or saw through it.

The strike, or strike plate, is the rectangular piece of metal in the door frame that receives the bolt.  In a wooden frame, this piece will only be as strong as the wood it is attached to.  This is why it is important that the strike fasteners are long enough to reach the stud behind the frame.

The dust box goes inside behind the strike plate, inside the door frame.  A metal dust box makes it much more difficult to get a tool behind the end of the bolt – a very important function in terms of burglary resistance.

On a steel door frame the strike plate becomes less important, but it is still important to guard the end of the bolt as effectively as possible.

The cylinder collar is the washer-like ring that surrounds the cylinder and rests against the exterior surface of the door.   The best deadbolts have solid collars that spin freely if one tries to twist them off with pliers.   Cheap deadbolts have hollow collars that crush like a beer can when gripped by pliers.

Since key bumping videos are now widely available via the Internet, it is worthwhile making sure your locks are bump resistant; lock picking is more of an art, but some burglars are skilled in it, so pick resistance is worth having; and because cordless drills are inexpensive and readily available, drill resistance is a good thing, too.   Locks that are resistant to these three kinds of attacks have a UL Listing UL437 for Burglary Resistance and say so on their labeling.  Two deadbolts that offer UL437 burglary resistance as well as sturdy bolts, collars and provisions for strike reinforcement are the Schlage B600 series with Primus or Everest UL437 cylinder, and the Medeco D11 series with M3 series cylinder.

Rim Deadlocks

The terms “deadlock” and “deadbolt” are often used interchangeably.

Surface mounted deadbolts, AKA rim deadlocks, were once the industry standard.   Many locksmiths’ fortunes were made on the Segal 667 “jimmy proof” deadbolt with cylinder and latch guards, and, in fact, that locking system was often effective in keeping burglars out.  My personal preference for maximum locking strength (short of a multi-point lock) is a jimmy proof rim deadbolt and a tubular deadbolt on the same door.

Here is an illustration of the Segal vertical deadbolt:

A jimmy proof deadbolt, otherwise known as a vertical deadbolt, is the most effective kind of rim deadlock because it interlocks the door and frame in a way that few other locks do.

The other kind of rim deadlock is a horizontal deadbolt such as the Yale 112 (see below left).

The Yale 112 features a 1-1/2 inch throw deadbolt – ½ inch longer than what is normally available in a tubular deadbolt.

To achieve bump, pick and drill resistance in a rim deadlock, simply add a UL437 UL listed rim cylinder.  Protect the cylinder with a cylinder guard to increase security still further.

The weakest part of the rim deadlock is the strike when it’s installed into a wooden frame.  To help alleviate this weakness, install screws that are long enough to reach the stud behind the door frame.

On a metal frame, a rim lock strike can be very strong when it is installed correctly.

Mortise Deadbolts

There are two kinds of mortise deadlocks:

  • Small Body Mortise Deadbolts
  • Full Size Mortise Deadbolts

Small body mortise deadbolts are usually installed where most auxiliary locks are installed, six inches to a foot above the primary lock, maybe around 60 inches from the bottom of the door frame.  The lock case of a small body mortise lock is variable – that is, it is not standardized.

A small body mortise deadbolt can be a good choice for a wooden door, especially if it is a thicker-than-usual wooden door.  Since the lock is a good size metal box that gets tucked into an approximately 5 inch by 1/2 inch pocket carved into the wood, the lock utilizes the strength of the door to its best advantage.

Full size mortise deadbolts are installed in an “86 prep” (see illustration), which is a pocket located on a center line about 40 inches above the bottom of the door frame.  Unlike most other deadbolts, full size mortise deadbolts are intended for use as the primary – and usually the only – lock on any given door.  Full size mortise deadbolts are usually used on mechanical compartments, closets in corridors or other places where trim would be in the way.

Both small body and full size mortise deadbolts feature heavy duty mechanisms and strong, 1-inch projection bolts.  With the addition of a high security, UL437 UL listed mortise cylinder to add bump, pick and drill resistance, mortise deadbolts can provide a high degree of security.


Schlage L460 Series Small Body Mortise Lock


Avoiding Tailpiece Loss Syndrome

SFIC Tailpieces, A.K.A. Throw Members

Tailpiece Loss Syndrome is such a common occurrence in the door hardware industry that it is almost a joke.  It happens like this:

  1. The job specifies small format interchangeable core (SFIC) cylindrical locks
  2. The locks are shipped with separate tailpieces, often called ‘throw members’
  3. The installer (usually a contractor) installs the locks and throws the tailpieces away

This occurs so often that when I get a call from a customer who says, “I have a job where we installed all SFIC cylindrical locks…”  I finish the sentence for them, “… and the contractor threw the tailpieces away.”   That usually gets a chuckle, but there’s not much humor in it really, especially if the tails must be factory ordered with a lead time of several weeks and the inspection is tomorrow.

Nope, no fun.

To avoid losing the tailpieces this way, there are a couple of things you might do:

  • Get a responsible person (maybe you) to collect the tailpieces when the locks are delivered, or
  • Have the tailpieces shipped separately directly to you, or
  • Order cores with the locks and have the contractor install them and ensure they are working properly.  (They will need to have the tails to accomplish this.)

If you elect to order the cores with the locks and want to avoid the delays associated with waiting for an order of master keyed permanent cores, order construction cores.   Construction cores are temporary cores that are all keyed alike for use during the construction phase.  Typically hardware re-sellers stock construction cores or they are readily available from the factory, so they are usually deliverable fairly quickly.


Locking People In

I often get a request to help create a system that locks people in.  People want to lock children inside a daycare center, students inside a “Time-Out” room, babies inside a nursery in a maternity hospital or patients inside, for example, an Alzheimer’s disease in-patient facility for their own good.

“Well, what if there’s a fire?” I ask.

That’s really the issue.  If we are keeping them in, how are they supposed to get out in the event of a fire?  Yet, except when there is a fire or other emergency that renders the building unsafe, it is in their best interest if they are kept inside.

Often, people simply want to lock people in with an electromagnetic lock or other device.  Since this is certainly a violation of life safety code, any injury that may result would be uninsurable and could invite litigation.

I discuss delayed egress systems in depth in another article (click here to read).     A delayed egress system is really the right way to do this, since it is actually covered in the NFPA 101A Special Locking Arrangements section of the fire safety code, but it is fairly inconvenient to use.  To get out without setting off an alarm users must use some kind of bypass request to exit switch like a keypad, card reader or key switch – much less convenient than, say, simply pushing a door open via the push pad on an exit device.

The gist of a delayed egress system is that, after a short ‘nuisance’ delay, the lock sounds an alarm for fifteen seconds and then lets the person out.  That means that authorities on the secured premises have fifteen seconds to get to the exit and prevent unauthorized egress.

Where unauthorized egress is not a life threatening prospect, therefore, a delayed egress system is perfectly adequate.  However, when a person’s life may depend on being kept inside their care facility, a more complex solution maybe required.

A great solution for Alzheimer’s or other dementia care facilities is the WanderGuard system by Stanley.  This system is designed for Alzheimer’s and other health care facilities where unscheduled patient departure is an issue, and covers other needs with fall monitoring and patient call capabilities.  Patients are fitted with bracelets that serve as tracking and communication devices.  As one might expect, such a system is not inexpensive and a bit on the overkill side for use in a day care center or maternity facility.  To physically keep people inside the facility, the WanderGuard system is designed to interface with delayed egress locks.

I think that the WanderGuard system would be a good choice for use in maternity ward nurseries as well.

The situation is more challenging when you have a day care center or a “Time-Out” room.

I had heard that Schlage was coming out with a mechanical time out lock, but a search as of today renders only the same Time-Out Room solution:  An electromagnetic lock with a momentary pushbutton.  The troublesome child is forced into a room, the door is shut, and then the teacher or other disciplinarian must physically press the momentary contact pushbutton to keep the magnetic locked locked.  As soon as the teacher lets go, the child is free.

As long as the button is momentary, I have no problem with this idea.  Should there be a fire or other life safety emergency, even if the teacher panics and runs away, leaving the child in the Time Out Room, the child will still be able to leave the room and exit the building.

The right way to prevent the kids in a daycare center from running out of the building and into the street without permission is with a delayed egress system.  True, it may be cumbersome to punch in a code on a keypad or present a proximity card for authorized egress, but delayed egress systems can be easily deactivated for periods of time, say, for drop off and pick up.  A delayed egress system is more expensive than, for example, an electromagnetic lock connected to the fire alarm system for safety.  But if you run the scenario of a fire in your mind, the fire alarm interface to the electromagnet malfunctions, panicked children and day care providers flinging themselves against an illegally locked door, too crazed with fear to think – suddenly a delayed egress system makes a lot more sense.

There is really only one place you can really lock someone in, and that’s in a jail or prison.  Otherwise there must be some provision to let them out – for safety’s sake.