Basics of Architectural Hardware
All locks are not created equal. They come in
many types, designed to perform a range of functions
and provide different levels of security. While
their primary purpose is always security, locking
needs will vary between a storage closet and a
Types of Locks
The main types of locks used commercially include
mortise, cylindrical, and rim. These designations
are based on the design of the lock, how and where
it engages, and how it is mounted to the door.
Mortise locks are generally considered the heaviest
duty products in the marketplace. They are typically
used in area of high traffic or heavy commercial
usage, where greater security is required. A mortise
lock is installed in a mortised pocket in the
door, with the housing of the lock contained in
the door. The cylinder is screwed through the
skin of the door directly into the metal lock
case, with only the cylinder head and spin ring
projecting from the face of the door. The lock
case may contain a dead bolt as well as the normal
dead latch for added strength and security.
Cylindrical locks are a simpler design installed
in two intersecting holes in the door. Normally
a 2-1/8" hole through the face of the door
intersects either a 7/8" or 1" diameter
hole from the edge. The cylinder is contained
in the outside knob or lever, away from the surface
of the door.
Rim locks are mounted to the inside surface of
the door, with a cylinder installed on the outside
surface in a hole bored through the door. They
typically have either a spring latch or dead bolt
operation, engaging a strike mounted to the frame
around the door. There are several types of dead
bolt mechanisms found on rim locks.
Lock cylinders in these and all locks may be
designed for standard keys readily available at
local hardware stores or controlled access/high
security keys, which are available only from the
manufacturer and selected locksmiths.
There are other mechanisms that can be considered
under locks, such as hospital latches and exit
devices. These are all useful varieties with specific
purposes or applications, and for this article
they will be considered from the standpoint of
lock function as variations in trim. Other lock
varieties, such as cabinet locks and padlocks,
will not be discussed.
Most electrical and electrified products are
actually electrically operated mechanical locks
and also will not be explored in further detail
here. These include electromagnetic locks, alarmed
or delayed exit devices, electric latch releases,
auxiliary alarm locks, touch keys, card readers,
keypads and other electrified means of activating
or controlling a lock. In most cases, the outside
lever is unlocked by a solenoid instead of a key,
although a key can provide an override or safety
feature. The main benefit of electronic access
control is a more flexible and higher level of
key control than the typical mechanical key system.
Not all locks function the same way. Commercial
cylindrical and mortise locks may have several
different functions to suit almost every combination
of convenience and security requirements. The
most common include passage, privacy, office,
entry, classroom, and storeroom, named after their
most typical applications.
Passage sets are not locks in the true sense
of the word, but incorporate a lever or knob on
either side of the door and a latch to hold the
door shut. There is no provision for a key, as
no lock cylinder is included.
Privacy locks are the type used in a public restroom,
or perhaps a residential bedroom or bathroom.
They contain no cylinder and do not have a key.
However, they can be locked from the inside for
privacy, usually by a pushbutton built into the
knob or lever. They generally include a provision
for emergency access from the outside, often using
a small screwdriver or pin to unlock the outside
knob or lever through a hole in the trim. Hospital
privacy latches have thumb turns on both sides
so a nurse or attendant can gain entry to a patient's
bathroom quickly in an emergency.
Office locks are locked from the inside by a
pushbutton. The outside lever or knob remains
locked until unlocked with a key from the outside
or by rotating the inside lever trim. The inside
knob or lever is always free for immediate exit.
Entrance or entry locks maybe locked by pushing
and turning a button and are unlocked by key until
the inside button is manually unlocked. They are
also available with pushbutton locking, in which
pushing the button locks the outside knob or lever
until it is unlocked by key or by turning the
inside knob or lever. The inside knob or lever
is always free for immediate exit.
Classroom locks(maintained)are always locked
and unlocked from the outside by key. The inside
knob or lever is always free for immediate exit.
Storeroom locks (momentary) have a fixed outside
knob or lever, and the latch is retracted by the
key from the outside. The inside knob or lever
is always free for immediate exit.
Making the Grade
Locks are available in different grades, which
relate to their construction and durability. These
grades are a measure of application suitability.
Most commercial applications require either Grade
1 or Grade 2 locking products. Because security,
protection from vandalism, durability under heavy
usage and other considerations are important,
the greater strength of Grade 1 locks makes them
the suitable choice for demanding applications.
Grade 2 products are adequate for lighter duty,
such as storage closets or doors where security
is less of an issue than simply excluding people
in general. They will keep people from walking
through a door, but they provide much less protection
against deliberate force than Grade 1 products.
ANSI/NHMA standards, monitored by independent
testing laboratories, separate Grade 1 from Grade
2. Typically, Grade 1 locks must meet twice the
requirements of Grade 2. In cycle tests for example,
a Grade 2 lock need only function for 400,000
cycles, while a Grade 1 lock must meet at least
800,000 cycles. Some manufacturers regularly test
beyond that limit into the millions of cycles.
Even among locks promoted as Grade 1, there can
be some differences. For mortise locks, ANSI A156.13
makes distinctions between Grade 1 Operational
and Grade 1 Security. The section includes a distinct
operational test that encompasses everything from
cycling to finish testing of mortise locks. A
separate listing covers security grading.
When choosing a Grade 1 mortise lock, it is important
to know whether the rating given is for security,
operational or both. Sometimes, the higher rating
is available only as an expensive up-charge. A
lock with concealed cylinder trim may be Grade
1 operational and Grade 1 security, while one
with an exposed cylinder may be only Grade 2 security.
One of the most difficult requirements to meet
for Grade 1 security is a cylinder wrenching requirement,
in which a cylinder must withstand (120 ft. lbs)
of torque. Here, a weak point of many mortise
lock designs is the cylinder attachment to the
lock case. The screw that fits into a groove on
the side of the cylinder will either bend or cut
a groove in the cylinder body and allow the cylinder
to be threaded out. Another security test is a
3,600 lb. pull test applied to the cylinder. A
concealed cylinder cannot be accessed for these
For most other types of locks, both security
and operational aspects are included under a single
grade. ANSI A156.2 Series 4000 is the standard
for bored-in locks and latches. While only an
operational grade, it includes some considerations
such as lock lever torque, vertical impact load
on the knob or lever, and other destructive tests.
Because the cylinder projects from the door, it
is more vulnerable to attack than a mortise lock
and is not really considered a security item.
Unlike some other hardware, which is available
in listed and non-listed versions, most commercial
locks are UL fire-listed. Most manufacturers have
different latch bolt lengths available and have
listed them so they can be used on both fire-rated
and non-fire-rated doors. However, different products
are listed with different sizes of door, depending
on such variables as latch type and size. When
used in a fire-rated application, each product
should be checked in the UL Building Materials
Directory to see what its listing actually covers.
What Type to Use?
Typical products available as Grade 1 include
cylindrical key and lever locks, mortise locks,
heavy-duty mortise, auxiliary deadbolts, and the
locks used with electronic or other access control
For most high-traffic areas, such as schools,
heavily used offices, stores or other public buildings,
a Grade 1 mortise lock is preferred. Because its
case is much larger than that of a cylindrical
lock, it can be built to incorporate parts with
thicker cross-sections and greater strength.
An alternative would be a Grade 1 cylindrical
key and lever lock, which is probably the most
popular for retrofitting because little or no
additional prep is required. For example, converting
from a cylindrical knob set to a lever in order
to meet ADA requirements usually entails drilling
only two holes. To achieve higher security where
heavy use or abuse is expected, combine the Grade
1 cylinder lock with an auxiliary deadbolt, providing
this combination is allowed by the local building
An advantage of a mortise lock in these situations
is that mortise locks are available with a deadbolt
as an integral part of the lock case. This combines
security with ease of operation, because of dual
retraction. From the inside, when the door is
locked and the deadbolt is extended, simply operating
the lever retracts both the latch bolt and deadbolt
simultaneously. From the outside, the key will
open both in sequence, retracting first the deadbolt
and then the latch bolt as the key is rotated
The trim used with a lock should be built as
strong as the rest of the lock. Lever trim, which
is becoming universal because it meets ADA requirements
and is easier for people to use, is also subject
to a wide variety of constructions and strengths.
Mortise locks typically use either forged or cast
levers, both of which are quite strong.
Whatever type of lock the application requires,
it is sure to be available from the wide variety
of types now on the market. A suitable choice
will consider the requirements for security, durability,
usage demands, building codes and accessibility