Two Electromagnetic Locking Devices, Two Very Different Installation Realities
This article helps contractors, facility managers, and security consultants decide between a shear lock and a surface-mounted electromagnetic lock (maglock) before the door gets hung. Both devices hold a door closed using magnetic force, but they differ in how that force is applied, what the door and frame need to look like, and what happens when the physics of a real opening work against a poorly chosen device. Getting this decision wrong means rework, code questions, or a device that simply does not hold.
What Is a Shear Lock vs. a Surface Maglock?
A surface maglock works by direct face-to-face attraction between an electromagnet mounted on the frame (usually the header) and a steel armature plate mounted flush on the door face. The holding force is perpendicular to the door face. When power is applied, the two surfaces pull together and the door is held closed.
A shear lock (sometimes called a shear maglock) works differently. The electromagnet and the mating armature are designed so that force is applied in shear -- parallel to the door face rather than perpendicular to it. The armature seats inside or flush with the lock body, and lateral loading is what provides the holding strength. This geometry makes shear locks far more resistant to pry attacks and better suited to doors where a direct pull-out force would compromise holding integrity.
The Frame and Header Condition Decides More Than You Think
Surface maglocks require a flat, solid header surface large enough for the electromagnet body and the armature bracket. On standard hollow metal frames with a flat soffit, this is usually straightforward. Problems appear when:
- The frame has a narrow or sloped header profile
- The door is on a storefront aluminum system with minimal header depth
- The opening is a pair of doors with no center post (no surface to mount to at the typical location)
- The door has a heavy-duty closer arm that conflicts with the maglock body footprint
Shear locks are typically recessed or semi-recessed into the frame header or the door edge, which means they need adequate frame steel and correct cutout prep. If the frame is not pre-prepped or cannot be field-modified without compromising its rating, the shear lock option may be off the table before the conversation even starts.
Door Swing Direction and Pull Force Matter
Surface maglocks on inswinging doors see pull force applied in the same axis as the door swing -- the occupant pushes against the door in the same direction the magnet releases. This is generally acceptable and the most common configuration. On outswinging doors, however, a surface maglock faces peel-and-pull loads from the outside, which can dramatically reduce effective holding force compared to the rated spec. Shear locks handle outswing conditions better because the holding geometry does not change with swing direction.
Double-egress pairs and 180-degree swing doors create additional geometry problems for surface maglocks. Shear locks are often the cleaner answer in those scenarios.
Code and Life-Safety Considerations
Both device types are electromagnetic -- meaning both are fail-safe (they release when power is removed). This is the defining code requirement for maglocks on most egress doors: the device must release on any of the following signals:
- Fire alarm activation
- Loss of power
- A listed release method at the door (switch bar, motion sensor, or request-to-exit device)
One critical point that applies equally to both types: a push button alone is not a compliant release method. A switch bar integrated into the door hardware or a motion-activated release is required where the device is the only means of egress control. This rule does not change based on which electromagnetic device you choose.
On fire-rated doors, neither a surface maglock nor a shear lock substitutes for positive latching hardware. A maglock holds a door but does not latch it. Fire-rated openings require a listed latching device -- typically an exit device or mortise lockset -- in addition to any electromagnetic hold. Your fire alarm interface must release the maglock and confirm the latching hardware can close and latch independently.
Security and Holding Force
Shear locks typically offer higher holding force in a smaller physical footprint and resist pry attacks more effectively than surface maglocks. In high-security applications -- data centers, pharmacy enclosures, server rooms -- shear locks are generally preferred. Surface maglocks are widely used and reliable in moderate-security environments like office corridors, school interior doors, and retail stockrooms where attack resistance is not the primary concern.
Installation Complexity and Long-Term Service
Surface maglocks are field-serviceable with standard tools. Alignment between the magnet body and the armature is visible and adjustable. Shear locks involve frame prep that must be done correctly the first time -- misalignment that is not visible on the surface can cause intermittent holding failures or armature wear that only shows up months later.
For retrofit projects where the frame is already in the wall, confirm the header construction before specifying a shear lock. A surface maglock with a properly specified Z-bracket or offset armature kit often solves a retrofit problem faster and with less risk to the existing frame condition.
Which Opening Gets Which Device
- Standard inswing, hollow metal frame, office or school corridor: Surface maglock is the efficient choice.
- Outswing or double-egress pair: Evaluate shear lock first.
- High-security or attack-resistant requirement: Shear lock.
- Storefront aluminum with narrow header: Confirm frame depth before specifying either; surface maglocks often need a bracket adapter.
- Fire-rated opening: Confirm latching hardware is present regardless of which electromagnetic device is used.
- Retrofit with existing frame: Surface maglock is usually lower risk unless security requires otherwise.
Get the Right Electromagnetic Hardware for Your Opening
DoorwaysPlus.com carries electromagnetic locking hardware suited to commercial, institutional, and industrial openings -- from surface maglocks with integrated armature bracket kits to shear locks for high-security and outswing applications. If you are working through a hardware schedule or access control drawing and need help matching the device to the opening condition, our team can assist with product selection, wiring guidance, and code compatibility. Visit DoorwaysPlus.com to shop or request a quote.