When selecting a mortise lock for your door, it's crucial to determine whether the door is left-hardware (LH) or right-hardware (RH). This classification affects compatibility with ANSI (American National Standards Institute) and EN 12209 Mortise Lock. Below, we explain how to identify the handing of a door and choose the correct lock type.

1.Determining Door Handing (Left-Hand vs. Right-Hand)

The handing of a door refers to the direction it swings and the location of the hinges. Here’s how to identify it:

Method 1: Standing Outside the Door (Exterior Side)

Stand outside the door (the side where the key is inserted).

Observe the hinge position:

Hinges on the LEFT + Door swings AWAY from you (push to open) → Left-Hand (LH)

Hinges on the RIGHT + Door swings AWAY from you (push to open) → Right-Hand (RH)

Hinges on the LEFT + Door swings TOWARD you (pull to open) → Left-Hand Reverse (LHR)

Hinges on the RIGHT + Door swings TOWARD you (pull to open) → Right-Hand Reverse (RHR)

Method 2: Using the "Keyhole Test" (For Existing Locks)

If the door already has a lock, check the keyhole orientation:

Keyway (key slot) on the LEFT → Typically LH door

Keyway on the RIGHT → Typically RH door

2.ANSI Mortise Locks vs. EN 12209 Mortise Lock

ANSI Mortise Locks (Common in North America)

Follow ANSI/BHMA standards with fixed handing (LH or RH).

The lock mechanism is hardware, meaning you must order either a LH or RH lock.

Common in commercial and residential doors with thicker doors (1-3/4" or more).

EN 12209 Mortise Lock (Common in Europe & Worldwide)

Use a standardized Euro profile cylinder (EN 1303 standard).

Most Euro cylinders are non-hardware, meaning the same cylinder works for LH and RH doors.

The lock body may still require handing, but the cylinder itself is universal.

3. How to Choose the Correct Lock

Key Considerations:

For ANSI Mortise Locks: Always confirm handing before purchase, or change handing per installation if needed.

For EN 12209 Mortise Lock: Check if the lock body requires handing (some do, but the cylinder does not).

Conclusion

ANSI mortise locks are hardware, so you must choose LH or RH.

EN 12209 Mortise Lock are typically non-hardware, making them more versatile.

Always verify the door’s handing before purchasing a lock to ensure proper fit and function.

By following these guidelines, you can confidently select the right lock for your door, whether it follows ANSI or Euro standards.

Diagram

mortise lock

EN 12209 Mortise Lock

ANSI Mortise Locks