Quick Summary

The word rim causes more confusion in commercial door hardware than almost any other term, because it describes a mounting method rather than a product. Ask ten people what a rim lock is and you will get answers ranging from a Victorian box lock to a modern exit device.

Both are correct, and that is the problem. This guide sets out what rim actually means, where it turns up on commercial doors, and what you need to know when ordering parts for it.

What Is a Rim Lock?

A rim lock is a lock whose body is mounted on the surface of the door rather than buried inside it.

Everything else follows from that. The door needs through holes rather than a routed pocket. The lock can be seen and reached without taking anything apart. Servicing happens with the door hanging, not with the lock case pulled out of the edge. And the lock sits proud of the face, which is why rim hardware is specified where appearance matters less than access.

Is a rim lock an old fashioned thing?

The historic surface mounted box lock is where the name comes from, and it still appears on period buildings. In current commercial specification, though, rim describes a mounting method used on thoroughly modern hardware, most visibly on exit devices.

So a rim device on a fire exit in a new building and a rim lock on a church door from 1880 share a principle and nothing else.

How Is a Rim Lock Different From a Mortise Lock?

A mortise lock lives inside a rectangular pocket cut into the edge of the door. A rim lock lives on the surface. That changes the preparation, the servicing, the security profile and the parts list.

Neither format is better in the abstract. A mortise lock buys concealment and a heavier mechanism inside the door. A rim device buys access, simpler preparation and faster servicing. Our comparison of mortise and cylindrical locks covers the third format in the same terms.

Can a rim device replace a mortise lock on the same door?

Sometimes, but it is a door preparation question rather than a hardware question. The mortise pocket does not disappear when the mortise lock comes out, and a rim device fixes through the face in a completely different pattern. Expect a filler plate and new fixing positions rather than a straight swap.

Where Do You Find Rim Hardware on a Commercial Door?

Overwhelmingly on exit doors, as rim exit devices.

A rim exit device latches into a strike mounted on the frame, which makes it the simplest of the four exit device configurations. There are no rods running to the head and sill, no lock case in the door edge, and nothing concealed inside the door. For a single door with a frame to latch into, it is the default choice.

The second place the word turns up is on the cylinder. A rim cylinder is the format used to key a rim device from the secure side. Our rim exit device guide covers the devices themselves in detail.

When is a rim device not the right choice?

On a pair of doors with no mullion, where there is nothing in the middle for a rim latch to engage. On a door that has to latch top and bottom for fire performance. And where the aesthetic specification rules out surface mounted hardware. In each of those, a vertical rod or mortise configuration takes over, as our concealed vertical rod guide covers.

What Is a Rim Cylinder and How Does It Attach?

A rim cylinder is a cylinder designed to be held against the outside face of the door by a backplate fitted on the inside, rather than threaded into a lock body.

The sequence is the clue to how it works. The cylinder goes through the door from outside. The backplate goes on behind it. Screws through the backplate pull the cylinder tight against the face. A tailpiece or cam on the back of the cylinder then reaches into the device and operates it.

Why does the backplate matter so much?

Because it is the only thing holding the cylinder in the door. A mortise cylinder is held by its own thread in the lock. A rim cylinder is held by a plate and two screws, and if those loosen the cylinder can turn or move in the hole.

A cylinder that spins when a key is turned is a backplate problem far more often than a cylinder problem, and the backplate is a stocked item in its own right.

What Does the Cam or Tailpiece Do?

It is the link between the cylinder and the mechanism. Turning the key turns the plug, the plug turns the cam, and the cam moves whatever the device needs moved.

Cams are not universal. The shape, length and orientation have to suit the device the cylinder is driving, which is why cams are listed as separate parts rather than assumed. Fitting a cylinder with the wrong cam gives you a key that turns smoothly and achieves nothing.

Does the keyway have to match the rest of the site?

If the building runs a key system, yes, and that is a decision made at order time rather than afterwards. A rim cylinder can be supplied to the site keyway so that existing keys work, which is usually preferable to adding another key to a bunch. Our key systems guide covers how that is organised.

What Strike Does a Rim Lock Need?

One positioned for a surface mounted latch, which is not the same as a strike for a mortise or cylindrical lock.

A rim latch approaches the frame from the face of the door rather than from inside its edge, so the strike has to present its opening in a different plane and at a different depth. Rim strikes are listed as their own family for exactly that reason.

On a pair of doors the picture changes again. The inactive leaf has to present something for the active leaf to latch into, which is where double door strikes and mullions come in.

Can the strike be electrified?

Yes, and it is one of the most common ways to add access control to a rim device. The electric strike replaces the fixed strike in the frame, the device stays as it is, and the opening gains remote release without touching the door. Our electric strikes guide covers the selection, and our strike plate guide covers the mechanical version.

Is a Rim Lock Secure Enough for a Commercial Door?

On the right door, yes, and it is used on millions of them.

The honest answer has conditions attached. Surface mounted hardware is visible and reachable, so the fixings matter. Through bolting rather than wood screws, a sound backplate behind the cylinder, and a strike that is properly anchored in the frame are what make the difference between a rim device that resists attack and one that does not.

The other factor is that a rim exit device on an exit door is usually on the secure side of the opening with no trim outside at all. There is very little to attack, because there is nothing out there to grip.

What about the cylinder as a weak point?

It is the component most exposed on the outside face, and that is worth designing around. Cylinder guards, recessed trim and the backplate arrangement behind the door all exist to make the cylinder harder to attack. On an opening with a history of attempts, those are the parts to look at rather than the device.

What Fails on Rim Hardware?

None of those is a device replacement. The point of rim hardware is that the parts are reachable, so the repair is usually a component swap with the door still hanging. Our panic bar parts guide lists the components for the exit devices most of this applies to.

What should you confirm before ordering rim parts?

Five things. The device series, from the stamping. Whether the part is for the device or the cylinder, because they are separate orders. The cam type where a cylinder is involved. The keyway, if the site runs a key system. And the finish, because rim hardware is visible.

If the cylinder format itself is the open question, our mortise cylinder and rim cylinder comparison is the quickest way to settle it, and the exit device terminology guide covers the naming.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

Quick Summary

Maglock installation looks like the simplest job in electrified hardware. There is no latch, no strike cutout, no mortise pocket, and the two halves simply have to meet. That is exactly why it gets rushed, and why so many of them end up holding at a fraction of their rating.

This guide covers the mechanical mounting, the power side, the egress arrangements that have to accompany it, and the faults that follow from getting any of the three wrong.

What Does a Maglock Installation Involve?

Three separate pieces of work that have to be planned together.

The mechanical part is mounting the magnet to the frame and the armature to the door so that the two meet flat and square. The electrical part is delivering the correct voltage to the magnet continuously, because a maglock is only locked while it is energised. The third part is everything that lets people out, because a lock that holds by power needs a defined way of letting go.

Treating any of the three as a follow up job is where maglock installations go wrong. The egress arrangement in particular dictates what else goes on the door, and that is easier to design in than to retrofit.

Is a maglock different from an electric strike in installation terms?

Completely. An electric strike goes into the frame and leaves the door untouched. A maglock puts hardware on both the door and the frame, carries its load across the joint between them, and needs power running the whole time the door is locked. Our electric strikes guide covers the alternative where the door preparation is the deciding factor.

Where Does the Magnet Go and Where Does the Armature Go?

The magnet mounts on the frame, usually at the head on the stop side, and the armature mounts on the door so that it arrives against the magnet face when the door closes.

The reason that way round is practical. The magnet is the half that needs wiring, and the frame is the half that does not move. Putting the powered half on a swinging leaf means running conductors across the hinge line for no reason.

How accurately do the two faces need to meet?

Flat and fully in contact. A magnetic lock holds by surface contact, and anything that keeps the two faces apart reduces the hold disproportionately. A small gap, a layer of paint, a build up of dirt or a slight twist in the armature all take holding force away.

This is the single biggest difference between a maglock that performs to its rating and one that can be pulled open by hand. The parts are not usually at fault. The alignment is.

How Is the Armature Fixed to the Door?

Through the door, with the fixings sized for the door thickness, and with the armature left able to move slightly.

That last point surprises people. The armature is not meant to be rigid. It needs a small amount of float so it can settle flat against the magnet face even when the door does not present it perfectly square. Clamping it solid removes that ability and guarantees partial contact.

What holds the magnet to the frame?

A mounting pack sized for the installation, and on many openings a bracket. Not every frame presents a flat surface in the right place, and inward opening doors, glass doors and frameless arrangements all need brackets to put the magnet where it needs to be.

Mounting hardware is supplied as a kit for the same reason screw packs are supplied for locks. The fixings are part of the specification, not consumables from the van.

What Power Does a Maglock Need?

Continuous power, at the voltage the unit is listed for, delivered at the lock rather than at the panel.

Because a maglock is energised the whole time it is locked, its supply sizing is different from a fail secure electric strike that draws nothing until released. Every maglock on a system contributes continuously to the load, which matters most when the building is running on battery backup.

Does the installation need a power transfer?

Only if something on the moving leaf needs power. The magnet is on the frame, so a plain maglock does not. The moment an electrified lock, an exit device with latch retraction or a door mounted sensor joins the opening, conductors have to cross the hinge line, and that is a transfer job. Our power transfer guide covers the options.

What Else Has to Be on the Door Before a Maglock Is Used?

This is the part of a maglock installation that is not optional and not a hardware preference.

Codes treat electrically locked egress doors as a special case, because the lock has no mechanical release. The conditions typically attached include a manual release device on the egress side, release of the lock on loss of power, and release on activation of the fire alarm system. What is required on a specific opening is decided by the authority having jurisdiction.

The practical consequence for the installer is that a maglock is never a single product on a door. It arrives with a release arrangement, and the arrangement is as much part of the installation as the magnet.

Does a motion sensor count as the release?

Sometimes, within conditions, and never as the only element. A request to exit sensor above the door can form part of a designed release arrangement, but what is permitted varies and the sensor is one component of a solution rather than the solution itself. Our request to exit sensor guide covers how those units behave and where they are mounted.

Where a door needs to hold briefly before releasing, that is delayed egress, which is a separate function with its own conditions. Our delayed egress guide covers it.

How Do You Monitor a Maglock Once It Is Fitted?

With a door position switch, and ideally with bond monitoring from the lock itself where the unit offers it.

The distinction matters. The access control system knows it energised the magnet. It does not know whether the door actually closed, whether the armature made contact, or whether somebody has propped the leaf. A door position switch answers the first of those, and it is the component most often left out of a maglock installation. Our Wiegand 26 bit guide explains the format, wiring, limits and OSDP.

Flush or surface mounted switch?

Flush where the door and frame can be drilled and the opening is interior and protected. Surface mounted where drilling is not practical, where the opening is exterior, or where a heavier duty unit is wanted on a door that takes abuse.

Our door position switch guide covers how the switch and the request to exit signal work together on a monitored opening.

Why Does My Maglock Not Hold Properly?

Nine times out of ten the answer is contact rather than current.

Working through that table in order resolves most complaints without replacing anything. A maglock is a simple device, and simple devices fail for mechanical reasons.

Can a maglock be mounted on a door with a closer?

It usually has to be, because the door needs to arrive at the magnet reliably. What matters is that the closer brings the leaf fully home. A door that stops a few millimetres short will energise the magnet with no contact at all, which looks like a lock failure and is a closer adjustment. Our door clearance guide covers the related measurements around the opening.

What Changes on an Exterior Opening?

Water, temperature and corrosion, all of which attack the contact surfaces that the lock depends on.

Weatherized units exist for exactly this reason. On an exterior door the magnet and armature faces are exposed to rain driven across them and to condensation forming on cold metal, and ordinary steel surfaces will discolour and eventually pit. That pitting reduces contact area, which reduces holding force.

Does an exterior maglock need different maintenance?

Yes, and it is simple. The faces want checking and cleaning periodically rather than after a complaint. A maglock on an exterior door that has not been looked at in three years is usually holding at well below its rating, and nobody will know until somebody pulls on it.

What Should You Confirm Before Ordering a Maglock?

Six things, and the first three come off the opening rather than the specification.

Whether the door is interior or exterior, because that decides weatherized or standard. The door thickness, because the through fixings are sized for it. Whether the door swings in or out, because that decides whether brackets are needed. The voltage available at the opening. Whether monitoring is required, and of what kind. And what the egress arrangement will be, because that is the part that has to be designed rather than ordered.

What if the opening already has an exit device?

Then the maglock may not be the right answer at all. A door that already latches mechanically and releases from the inside has most of what a maglock is being asked to provide, and adding one can complicate the egress picture rather than simplify it. For the full component breakdown of magnetic locks themselves, our electromagnetic lock parts guide covers what is supplied separately, and our fire rating guide covers what changes on a rated opening.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.