Rim Lock vs Mortice Door Knobs

Author: Carl Benson

Carl is the founder of Suffolk Latch Company, with a background in engineering and over 20 years’ experience in home hardware. He works closely with suppliers and designers alike to develop quality ironmongery that stands the test of time. Read my full bio.

Rim Lock vs Mortice Door Knobs

Rim lock vs mortice door knobs is an important distinction when choosing traditional door furniture. The two styles may look similar once fitted, but the lock or latch behind them is very different.

A rim lock is fitted to the face of the door and remains visible. A mortice lock or latch is recessed into the edge of the door and hidden from view. This difference affects the door knob set, spindle length, rose plates, fixing method and suitability for older doors.

If you are choosing door knobs for a traditional or period property, start by identifying the lock type before choosing the finish. You can browse suitable products in our Rim Lock Door Knobs Collection or view our wider Door Knobs Collection.

Table of Contents

What Is the Difference Between a Rim Lock and a Mortice Lock?

A rim lock is a surface-mounted lock fitted directly to the face of the door. The lock case remains visible and forms part of the appearance of the door. Rim locks are often found in Victorian, Edwardian, cottage and period properties.

A mortice lock is fitted into a recess cut into the edge of the door. Once installed, most of the mechanism is hidden inside the door. Only the faceplate on the door edge, the strike plate on the frame, the door knobs and any keyhole furniture remain visible.

The easiest way to tell the difference is to look at the inside face of the door. If there is a visible metal lock case fixed to the surface, it is likely to be a rim lock. If the mechanism is hidden inside the edge of the door, it is likely to be a mortice lock or mortice latch.

This matters because rim locks and mortice locks usually need different door knob arrangements. Choosing the wrong type can lead to poor fitting, short spindles, unsupported roses or a knob that does not sit correctly against the lock.

Rim Lock vs Rim Latch

A rim lock and a rim latch are similar because both are fitted to the face of the door, but they do not do the same job.

A rim lock normally contains two functions. It has a spring latch operated by the door knob, and a separate deadbolt operated by a key. This allows the door to latch closed during normal use and lock when needed.

A rim latch usually contains only the spring latch. It keeps the door closed but does not include a key-operated deadbolt. Rim latches are useful where a traditional surface-mounted look is wanted but key locking is not required.

If a door needs to lock with a key, check that you are choosing a rim lock rather than a simple rim latch.

Iron Bathroom Rim Lock

Large Iron Rim Lock

Mortice Lock vs Mortice Latch

The word mortice refers to the recess cut into the edge of the door. Both mortice locks and mortice latches are fitted into this recess, but they serve different purposes.

A mortice latch, often called a tubular latch, contains only the spring latch. It is used on doors that need to stay closed but do not need to lock. This is common on hallways, living rooms, dining rooms and other standard internal doors.

A mortice lock includes a locking function. A mortice sash lock contains both a latch and a deadbolt, so it can be operated by a door knob and locked with a key. A mortice deadlock contains only a deadbolt and is not operated by the door knob.

For door knobs, the most common internal arrangement is a mortice latch or mortice sash lock with a suitable backset. Door knobs usually need more backset than lever handles so there is enough clearance from the frame.

Rim Door Knobs vs Mortice Door Knobs

Rim door knobs are designed for surface-mounted rim locks. On the rim lock side, the knob normally sits directly against the lock case. On the opposite side, the knob fixes to the timber door, usually with a rose plate.

Mortice door knobs are designed for latches or locks recessed into the edge of the door. In this arrangement, both knobs usually fix to the timber face of the door and both sides normally have rose plates.

The spindle also differs. A rim lock door knob set usually needs a longer spindle because it must pass through the door and the rim lock case. A standard mortice knob spindle normally only needs to pass through the door and the latch or lock follower.

For a dedicated guide to this fitting type, read Rim Lock Door Knobs Explained.

Brass Bathroom Rim Lock

Large Brass Rim Lock

Door Thickness and Suitability

Door thickness is one of the main reasons rim locks are still useful in older properties. Many period internal doors are thinner than modern doors and were originally designed for surface-mounted locks.

Cutting a deep mortice into a thin old door can remove too much timber. This may weaken the door and leave very little material around the lock body. In these situations, retaining a rim lock can be more practical and more sympathetic to the original joinery.

Modern internal doors are usually better suited to mortice latches and mortice locks. They are generally thick enough to accept the lock body and are commonly supplied with mortice-style hardware in mind.

Before replacing a rim lock with a mortice lock, measure the door thickness and consider how much timber would need to be removed.

Period Doors and Original Joinery

In period properties, the existing door can often tell you what type of hardware was originally fitted. Look for old screw holes, paint shadows, keyhole positions, filled mortices and marks left by previous lock cases.

If a door originally had a rim lock, keeping that arrangement may preserve more of the door. It also avoids cutting a new recess into old timber, which can be difficult to reverse later.

This is particularly relevant in Victorian and Edwardian homes, where rim locks were commonly used on internal doors. A suitable rim lock with the correct rim door knob set can keep the traditional appearance while still providing reliable day-to-day use.

For wider period-property guidance, read Choosing Door Knobs for a Victorian House.

Internal Privacy vs External Security

Internal and external doors should be treated differently.

On internal doors, a rim lock or mortice lock is often used for privacy rather than serious security. Bedrooms, studies and home offices may need occasional key locking, while many internal doors only need a latch.

External doors need a higher level of security. Although rim locks were historically used on entrance doors, modern insurance requirements may expect a certified security lock, such as a British Standard 5-lever mortice lock or another approved locking system.

This does not always mean a traditional rim lock has to be removed from a period front door. In many cases, the rim lock can remain as part of the original door furniture while an additional certified lock provides the required security.

For more information on lock types and door knobs, read Door Knobs With Locks Explained.

Which Is Better: Rim Lock or Mortice Lock?

Neither is automatically better. The right choice depends on the door, property and level of security required.

A rim lock is often the better option for older or thinner doors, especially where preserving original joinery is important. It is also a natural choice for period interiors where the lock case is intended to be visible.

A mortice lock or latch is often the better option for modern doors where a concealed mechanism is preferred. It gives a cleaner appearance and is widely used with modern internal door construction.

For external doors, the decision should be based on security as well as appearance. A traditional rim lock may look right, but the door may still need a certified lock to meet insurance requirements.

What to Check Before Ordering

Before ordering door knobs, check the existing lock or latch carefully.

• Is the lock visible on the face of the door? If yes, it is likely to be a rim lock.
• Is the lock hidden inside the edge? If yes, it is likely to be a mortice latch or mortice lock.
• Does the door need to lock? A latch alone will not provide key locking.
• Is the door thick enough? Thin period doors may not suit a modern mortice lock.
• Is the spindle long enough? Rim locks usually need a longer spindle than mortice knob sets.
• Does the rose arrangement suit the lock? Rim locks normally need one knob to sit directly against the lock case.

If you are still unsure, start with the door and mechanism before choosing the finish. This is the safest way to avoid ordering the wrong door knob set.

3 Lever Sash Lock - 3 Inch Antique Brass

5 Lever Mortice Lock - 2.5 Inch Antique Brass

Related Reading

These supporting guides explain related door knob and lock choices in more detail:

• Door Knobs Explained: The Complete Guide
• How to Choose Door Knobs
• Rim Lock Door Knobs Explained
• Door Knobs With Locks Explained
• What Are Beehive Door Knobs?
• Wooden Door Knobs Explained
• Cast Iron Door Knobs Explained
• Antique Brass Door Knobs Explained
• Choosing Door Knobs for a Victorian House

Conclusion

The difference between rim lock and mortice door knobs starts with the lock itself. A rim lock sits on the surface of the door and usually needs a dedicated rim knob set. A mortice lock or latch is recessed into the edge of the door and normally uses a standard mortice door knob set.

For older or thinner doors, a rim lock can be the more practical and sympathetic option. For modern doors, a mortice latch or mortice lock is often the standard choice. Before choosing a finish, identify the lock type, measure the door and check the spindle and rose arrangement.

To choose suitable products, browse our Rim Lock Door Knobs Collection or our wider Door Knobs Collection.

FAQ

What is the difference between a rim lock and a mortice lock?

A rim lock is fitted to the surface of the door and remains visible. A mortice lock is fitted into a recess cut into the edge of the door, so most of the mechanism is hidden.

Which is better, rim lock or mortice lock?

Neither is always better. A rim lock is often suitable for period or thinner doors, while a mortice lock is common on modern doors where a concealed mechanism is preferred.

Are rim locks secure?

Rim locks can provide suitable privacy or light security on internal doors. For external doors, check your insurance requirements, as a certified security lock may be needed.

Can rim locks be used on front doors?

Yes, rim locks can be used on front doors, especially in period properties. However, modern entrance doors may also need an additional certified lock to meet security or insurance requirements.

Can I replace a rim lock with a mortice lock?

Yes, but it is not always the best option. Fitting a mortice lock requires timber to be removed from the edge of the door, which can weaken older or thinner doors.

What is the difference between a rim lock and a night latch?

A rim lock is normally operated by a pair of door knobs and may include a key-operated deadbolt. A night latch is a surface-mounted front-door lock that usually operates with an external cylinder and internal release lever.

Horizontal 3 Lever Sashlock - 6 Inch Aged Brass

Horizontal Bathroom Sashlock - 6 Inch Antique Brass