Basic Lock Terminology – Cylindrical, Tubular or Mortise? – FAQ About Locks

This article provides answers to some of the most frequently asked questions about locks. What are the differences between a cylindrical lockset and a tubular lockset? What is a mortise lockset? What does backset mean? What is a Grade 2 lockset? What is a rosette? The answers lie within!

Note: In this article we have used the words “knob” and “lever” interchangeably, as the same principles typically apply to both.

What is a Cylindrical Lockset?

A cylindrical lockset is designed to be installed through the door with a knob on either side that, when turned, will retract the spring latch. The main advantage of a cylindrical lock is that it is relatively quick and easy to install and it is a little more heavy duty than its tubular lockset counterpart because the lockset itself has a cylindrical housing which inserts into the door. The spring latch inserts into a slot at the edge of this cylindrical housing and interconnects with the retractors that will operate the latch when the knob activated.

This lock design is most common for commercial locksets, but there are some residential models that are of the cylindrical design.

What is a Tubular Lockset?

Like the cylindrical lockset, the tubular lockset is designed to be installed through the door with a lever on either side that, when activated, will retract the spring latch. With the tubular lock design, however, there is no cylindrical housing. A spindle attached to the outside part of the lockset passes through a follower (or hub) in the center of the latch and interconnects into the inside part of the lockset. It is this spindle that will operate the spring latch when the levers are activated.

What is a Mortise Lockset?

A mortise lock is set within the body of a door inside a large pocket or mortise. The typical mortise lock includes the lock body or box (the part installed inside the mortise cut-out in the door); the lock trim, which may be selected from many different styles of knobs or levers; and, if required, a keyed cylinder which operates the locking/unlocking function of the lock body. These locks were very common in North America before the advent of cylindrical bored locks, and they are still widely used in Europe.

In Canada and USA, mortise locks are still common in schools and government buildings because of their durability and the wide variety of locking functions available.

What is a Deadbolt Lock?

A deadbolt or a deadlock is a locking mechanism distinctly different from a typical cylindrical or tubular lockset because a deadbolt latch cannot be moved to the open position except by rotating the lock cylinder with a key (unlike the spring latch, which can be depressed by force.) This is why a deadbolt is much more resistant to forced entry than typical cylindrical or tubular locksets with spring latches. Most deadbolts typically include a cylinder on the outside and a thumbturn on the inside; however, double-cylinder deadbolts are also available for certain applications.

Deadbolts are typically used as companions with spring latch type locks on residential and commercial entry doors and apartment doors.

What is a Bore?

Bore refers to the lockset preparation in the door. In North America, almost all cylindrical and tubular locksets require a 2 1/8” diameter bore through the faces of the door and a 1” bore into the edge of the door.

What is Backset?

The backset is the distance from the edge of the door to the centre of the 2 1/8” bore. In Canada and USA, the two most common backsets for residential and commercial door locks are 2 3/8” and 2 3/4”. For some commercial and industrial applications, 3 3/4” and 5” backsets are
occasionally used to facilitate operation of door handles for personnel wearing bulky gloves or carrying cumbersome items.

What is a Latch Bolt (or Latch or Spring Latch)?

The latch bolt (or latch or spring latch) is the part of the lockset that fits into the edge of the door and that engages the strike plate in the frame, allowing the door to “latch” and stay closed.

What is a Strike or Strike Plate?

A strike plate is a metal plate with a hole that is affixed to a door jamb to accept the latch. When the door is closed, the latch extends into the hole in the strike plate and holds the door closed. The strike plate protects the jamb against friction from the latch and increases security in the case of a jamb made of a softer material like wood.

Most residential door locks include either a T-strike or full-lip strike whereas most commercial door locks include a standardized (ASA) strike that is compatible with all standard pressed steel (hollow metal) door frames. Deadbolts are equipped with a strike plate that has no lip.

What is a Rosette?

A door knob rosette is the decorative backplate attached to a door knob or lever that covers the 2 1/8” bore in a door. A wide variety of locksets are available that feature traditional round rosettes, square rosettes and new ultra modern trapezoid shaped rosettes, exclusive to DDH!

What Does Grade 1, Grade 2 and Grade 3 Mean?

There are several different specifications and numerical assignments that determine and classify the duty capacity, grade and performance of door locks (and door hardware in general) as Grade 1, Grade 2 or Grade 3. The details could fill a technical journal, so please use the following as a general guideline instead:

Grade 1 hardware is usually specified for heavy duty commercial, institutional or industrial applications. Hardware in this category is typically of heavy duty construction, is suitable for use in 3 hour fire rated assemblies and has also passed high volume cycle tests. Examples of some instances where Grade 1 hardware might be utilized are arenas, public buildings, hospitals, nursing homes, factories and high schools.

Grade 2 hardware is ideal for medium duty commercial, institutional or industrial applications. Hardware in this category is typically of sturdy construction and is suitable for use in 3 hour fire rated assemblies but some is limited for use in 1 1/2 hour fire rated assemblies. Examples of some instances where Grade 2 hardware might be utilized are apartment buildings, churches, offices, pre-schools, commercial buildings and retail stores.

Grade 3 hardware is suitable for residential applications and for small offices with low occupancy and low cycle usage. Most hardware in this category has usually not been tested for use in fire rated assemblies, but sometimes can be upgraded for use in 20 minute fire rated assemblies with the addition of accessories like steel fire sleeves for locks. Examples of some instances where Grade 3 hardware might be utilized are homes, cottages or small offices.

Buyers should know that an assigned higher grade certification of a specific lock is not always an indication of a higher quality product over another lock with a lesser grade certification or no certification. Sometimes, the only difference between a Grade 1 and a Grade 3 door handle or deadbolt is that one manufacturer elected to spend the tens of thousands of dollars required to test that specific product in order to obtain a higher grade certification rating whereas another manufacturer did not. Some door handles and deadbolts sold at “big box” stores are famous for advertising Grade 1 and Grade 2 certification ratings but the hardware has been manufactured in the same facility and to the exact same specifications as other door handles and deadbolts that have not been tested for any certifications. The visual evidence is always the best guide – if a lock looks and feels sturdy and solid, then don’t be too concerned with grade certifications unless you are in charge of procuring hardware for a high traffic government facility or public building where factors like fire rating and cycle usage are paramount.

If you have any questions with regards to door lock terminology, please feel free to reach out to a member of our Customer Service Team!