A rim exit device uses 1 edge latch, a vertical rod system uses 2 latches, and a mortise device combines 1 latch with a deadbolt for added security.
The correct channel depends on the opening, door construction, fire rating and latching duty: retrofit a standard single leaf with rim hardware, secure an unmatched pair with vertical rods, or specify a mortise case where the door edge can be prepared.
Choose the exit-device channel by opening geometry
Rim, surface vertical rod and mortise hardware differ in latch count, visible components and door preparation [S1][S3]. Rim hardware produces 1 latch point at the lock edge, surface vertical rod hardware produces 2 points at the head and floor, concealed vertical rod hardware also produces 2 concealed points, and mortise hardware uses 1 lock-edge latch plus a deadbolt [S1].
Rim devices suit single doors in standard hollow-metal or wood frames, including retrofit work without vertical-rod channels. They mount on the door face and engage a rim strike at the frame doorstop, which makes the mechanism comparatively accessible for service and replacement [S1][S2].
A matched pair of doors changes the decision. Rim devices need a fixed or removable mullion so that each leaf has a strike-receiving member. Vertical rods can instead secure each leaf to the head frame and floor, allowing both leaves to open without a center mullion [S3]. Mortise devices are generally suited to a single leaf or the active leaf of a pair where the lock edge is prepared for a fixed mortise case [S3].
Compare cost, appearance and installation effort
Rim hardware has the lowest relative specification cost because it requires surface mounting only, while surface vertical rod hardware is low cost but adds a floor strike, concealed vertical rod hardware is medium-high cost because of factory channels, and mortise hardware carries the highest relative cost because of the edge pocket [S1].
The appearance trade-off is straightforward: surface vertical rod hardware exposes 2 rods on the door face, whereas concealed vertical rod hardware hides the mechanism and rods inside the stile. Rim hardware also leaves the lock housing visible on the face, while mortise hardware places the lock case inside the door edge [S1][S3][S4].
Installation effort follows the same pattern. Rim hardware needs no door-edge pocket, surface vertical rods require a floor strike or threshold guide, concealed vertical rods require a mortise pocket plus top and bottom bores, and mortise hardware requires the edge case to be prepared before ordering [S1][S3][S4]. The architectural hardware schedule should therefore distinguish the frame, threshold and door preparation attached to each option.
Use vertical rods when pair security overrides rod visibility
Vertical rod systems retract a top rod and a bottom rod simultaneously when the crossbar is depressed. The upper bolt engages a strike in the head frame and the lower bolt engages a strike in the floor or threshold, creating 2-point latching on each leaf [S2].
This arrangement addresses the principal weakness of a rim device on an unmatched pair. With only 1 edge latch, a door panel can flex past the strike at mid-panel height, and a pair without an astragal can leave an opening that defeats positive latching [S1]. Surface vertical rods are therefore suited to paired doors without a center post and to security-oriented single doors where 2-point latching is required [S1].
The bottom connection is the weak service point. Dirt and grit can collect in the floor strike, carts and cleaning equipment can damage the rod, a new floor finish can alter strike height, and a leaf that drops on its hinges may no longer reach the strike. A failed bottom latch leaves the leaf secured only at the head [S3].
Use concealed rods for fire-rated pairs and restrained profiles
Concealed vertical rod devices retain 2-point latching while showing only the crossbar or touchpad on the push side. Their rods run through the door stile to top and bottom strikes, with the mechanism concealed within the leaf [S4].
Fire-rated pairs without a mullion are a primary application because each leaf must latch independently at the top and bottom into fixed elements. A rim device cannot provide the inactive leaf with a fixed jamb strike, while concealed vertical rods can engage the head frame and floor [S4].
Fire-door assemblies are offered in 20-minute, 45-minute, 60-minute, 90-minute and 180-minute ratings, and the selected exit device must be listed for the assembly rating. The complete assembly, including hardware and mullion arrangement, must match the certified listing [S4]. The trade-off is preparation and service: concealed vertical rods need factory channels and are harder to adjust or repair than rim hardware [S1][S3].
Specify mortise hardware when the door edge can be prepared
A mortise exit device places a lock case inside a pocket in the door edge while retaining surface-mounted panic hardware. The mechanism can combine the edge latch with a deadbolt, providing a security function beyond the basic positive latching of a rim device [S1][S7].
This option is appropriate when a concealed lock body and a high-security appearance outweigh the additional door preparation. The lock case must be cut into the edge before the device is ordered, and that preparation is less adaptable than a surface-mounted rim device [S3]. Mortise panic devices are also less common because both the door preparation and product design are more complex [S8].
Mortise hardware is not the automatic choice for every single door. A retrofit opening that lacks a suitable edge pocket may cost more to modify than to fit a rim device, while a door intended for direct factory manufacture can accommodate a fixed mortise case more efficiently [S3].
Match fire rating, egress function and maintenance exposure
Panic hardware is intended for immediate egress without a key, while EN 179 emergency escape hardware serves a different operating concept. The exit-device decision must therefore begin with whether the opening needs an EN 1125 panic bar or an EN 179 emergency handle before the rim, vertical rod or mortise channel is selected [S3].
Fire-rated and non-fire-rated devices differ in their operating arrangement, but a fire door assembly must retain positive latching. The exit device and the complete door assembly must be listed and labeled for the applicable rating, and not every concealed vertical rod model carries every rating label [S4][S5].
For service planning, rim devices have the broadest aftermarket-part availability and the easiest access to their mechanism. Surface vertical rods add a floor interface, concealed vertical rods add factory channels, and mortise devices add a fixed edge pocket [S1]. Track service records for bottom-strike engagement, floor-height changes, door drop, and paired-leaf alignment before adding an exit device to an approved-equipment schedule.