EM Lock Buying Guide: 300, 600 or 1200 lbs, and Which Bracket You Need
An electromagnetic lock (EM lock or maglock) is the most common lock used with access control systems in offices, clinics, labs and showrooms. It has no moving parts: an electromagnet on the door frame holds a steel armature plate fixed on the door. When power flows, the door stays locked; when power is cut by the access control, exit button or a fire signal, the door releases instantly.
This guide explains how to choose the right EM lock and the parts that go with it.
1. Choose the holding force
Holding force is how hard the lock resists the door being pulled open. It is written in pounds (lbs).
| Holding force | Approx. in kg | Typical use |
|---|---|---|
| 100–300 lbs | 45–135 kg | Cabinets, light internal doors, low-risk rooms |
| 600 lbs | ~270 kg | Most single office, cabin and glass doors |
| 1200 lbs (single or double leaf) | ~540 kg | Main entrances, heavy metal doors, double doors |
Rule of thumb: 600 lbs is right for most single doors. Choose 1200 lbs for main entrances, heavy doors or double doors (a double-leaf 1200 lbs lock holds both leaves).
2. Match the bracket to your door
The magnet mounts on the top of the frame and the plate on the door. On an outward-opening door with a wide enough frame, no bracket is needed. Otherwise:
- L bracket – for doors that open outward where the magnet cannot sit flush on the frame.
- Z + L bracket – for doors that open inward (towards the magnet side).
- U bracket – for frameless glass doors; it clamps the armature plate to the glass without drilling.
- GG bracket – for glass-to-glass doors where there is no frame at all (glass door with glass side panel).
Not sure which you need? Send us a photo of the door on WhatsApp and our team will tell you.
3. Power supply
EM locks usually run on 12V DC. Use a proper access control power supply (such as the K80 type) rather than a simple adapter, so the lock releases cleanly and the system keeps working smoothly. Many supplies also have a battery backup option.
4. Fail-safe means the door opens when power fails
EM locks are fail-safe: if power is lost, the door opens. This is important for fire safety and is why EM locks are popular in commercial buildings. If you need a door to stay locked during a power cut, ask us about fail-secure locks such as drop bolts or strike locks with battery backup.
5. Exit button and feedback
- Every EM lock door needs a way out: an exit push button or no-touch exit switch on the inside.
- Locks with feedback/LED tell the access controller whether the door is actually closed and locked — useful for alarms and audit logs.
- Some models include a buzzer and timer that sound if the door is left open.
Complete kits save time
If you are setting up a door from scratch, a combo kit with the lock, bracket, power supply, exit button and card/fingerprint reader is easier than buying parts separately. See our combos and kits.
Frequently asked questions
Can an EM lock be used on a glass door?
Yes. Use a U bracket for frameless glass doors, or a GG bracket for glass-to-glass doors.
Is 600 lbs enough for a main door?
For most office main doors 600 lbs works, but for heavy metal doors, high-traffic entrances or double doors, 1200 lbs is the safer choice.
Will the door open during a power cut?
Yes, EM locks are fail-safe. Add a battery-backed power supply if you want the lock to stay powered during short outages.
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