Bored Locks

The definition from the locksmith dictionary says;

a lock for a door prepared with one or more
cross-bores and one or more edge-bores. 

A cross bore is a hole bored or drilled into the face of the door. 

The cross bore usually goes completely through the door but there are communicating door locks that don’t require the hole through the door, just into it. The edge bore is a hole bored or drilled into the edge of the door so that it intersects the cross bore.

There are some important features about the cross bore that need to be considered, especially if you are replacing an existing lock.

Backset is the distance from the leading edge of a door to the center of the cross bore.  Two dimensions are typical in the US, 2 3/4" and 2 3/8”.  There are other standard backsets that have been used and one that came close to being a standard is 5 1/2".

Another important dimension is the diameter of the hole used for the cross bore.  Most locks available in 2008 have a 2 1/8” diameter but there are other size requirements for some brands.  If you have a different diameter hole in your door that is too small, there is some good advice for redrilling the cross bore in the Redrilling a Door article.  If the cross bore is too large now your easiest option is to plug the hole and redrill it.

Most bored locks only require one of each type of hole, but there is a type of bored lock that requires more than one, the interconnected lock. 

There are two general types of bored locks;

A cylindrical lock has the locking mechanism in the part of the lock mounted via the cross bore.  You can check the type easily by holding the lock part that mounts through the cross bore and trying to lock it in your hand.  If the knob or lever won't turn, it is a cylindrical lock, if it will turn, it is a tubular lock.

The Tubular lock is typically a deadbolt that is mounted separately from the key-in-knob or lever lock.  The original intent of the deadbolt was to be a secondary locking device to be used when no one was occupying the building. 


There are two types of deadbolts, the single cylinder and the double cylinder.  The single cylinder only requires a key to operate it from the outside while the double cylinder requires a key from both sides of the door. 

Some municipalities have outlawed the double cylinder deadbolt because people have a tendency to lock them when they are in the building and that poses a hazard if there should be a fire or some other reason to leave quickly.  In a panic situation such as a fire very few people will have the presence of mind to get a key to unlock the door.  It also may be hard to find a key hidden near the door when the room is filled with smoke and fire.

Many locksmiths discourage the installation of double cylinder deadbolts because of this hazard but there is an alternative if you feel you require a double cylinder lock.  There are dead bolts on the market that capture the key inside and won’t release it until some other extra step is performed.  That typically should discourage not having a means of exit without consciously choosing to remove the key.

Knobs and Levers

The next type of bored lock is the key-in-knob or key-in-lever lock so typical in the US.  The same dimensional features are just as important with these types of lock and either type may be cylindrical or tubular in function.

The common shape has traditionally been a knob and the outside knob typically has a keyhole in it.  Along with the Americans with Disabilities Act mandates we have started seeing that tradition change.  It is becoming more common to see lever handles in these applications.

The most important feature to examine on these types of lock are the latch itself.  Check the article on latches for details.


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