Types of French Door Locks: How to Choose the Right Locking Mechanism

French doors use one of four locking arrangements — single-point deadbolt, mortise, flush bolt, or multipoint — and the right choice depends entirely on which leaf carries the active lock.

A French door that won’t lock usually isn’t broken; it’s mismatched. The active leaf swings, latches, and carries the keyed hardware, while the inactive leaf stays put with bolts at the top and bottom. Order the wrong mechanism for that active leaf and you’ll spend a weekend drilling a door you can’t return.

The four locking types below cover nearly every French door made for US homes. Match yours to the list, confirm your door’s existing preparation, and the choice makes itself.

The Four Types of French Door Locks

Single-point deadbolts and cylindrical locks suit standard bored doors, mortise locks recess into the door edge, flush bolts secure the inactive leaf, and multipoint locks drive several points into the frame from one handle.

• Single-point deadbolt or cylindrical lock: the active leaf carries the keyed or electronic lock, while the inactive leaf typically uses a dummy handle plus top-and-bottom flush bolts. Schlage advises boring one leaf for the primary lock and leaving the opposite leaf unbored.
• Mortise lock: a lock case recessed into the door edge that combines latch, deadbolt, and handles in one unit. Compatibility hinges on case dimensions, backset, faceplate, handing, spindle, cylinder, and strike alignment. A retrofit smart lock built for a standard deadbolt often won’t fit a mortise case.
• Flush bolts: the inactive leaf is held by manually operated bolts that extend into the head and sill. There’s no independent latch-and-strike, so a flush-bolted leaf can’t take a standalone smart lock.
• Multipoint lock: one handle-and-key mechanism drives several locking points into the frame — hooks, deadbolts, rollers, or a mix. SIEGENIA describes systems with three high-strength hooks and four adjustable mushroom cams, sized for both single and double doors.

Matching A Lock To Your Door’s Existing Preparation

Measure the door’s current preparation before ordering anything, because replacement hardware has to match the existing cutouts or you’ll be re-boring the door.

Write down door thickness, backset, faceplate size, lockcase dimensions, spindle height, cylinder type, handing, bore spacing, and strike position. A published Eurospec French-door data sheet from MILA specifies a 16 mm faceplate, 35 mm backset, and 92 mm/62 mm PZ centers across several hook-and-roller configurations — proof that these numbers vary by system and can’t be guessed.

Replacement multipoint locks must match the manufacturer’s geometry exactly. If your door already has multipoint routing and frame keeps, stay with multipoint; a conventional deadbolt is not a drop-in substitute.

Standard US bore preparation is the green light for a deadbolt or cylindrical lock, provided the inactive leaf is secured separately with correctly installed flush bolts. For exterior doors, prioritize weather-resistant hardware, aligned strikes, and a lock rated for the door material and exposure. A lock that needs force to operate usually points to hinge sag, door compression, or strike misalignment rather than a bad cylinder.

Glass-panel doors raise one extra decision. Schlage notes some homeowners choose a double-cylinder deadbolt for added resistance to access through broken glass, but local code and emergency-egress rules should be checked before going that route.

Smart Locks On French Doors: What Actually Fits

A smart lock belongs on the active leaf only, and only when the door’s existing preparation matches what the smart lock requires — the inactive leaf stays manual.

Most smart locks are engineered around a standard single-door deadbolt, so they aren’t automatically compatible with multipoint systems. Some multipoint mechanisms accept a compatible smart cylinder; others need the original mechanism to stay manual. That compatibility question goes to the hardware manufacturer, not the smart-lock box.

Schlage states its electronic and smart locks work with standard doors and install on French or double-entry doors the same way mechanical deadbolts do, as long as the door has the required standard preparation.

If you’re weighing specific models against your door’s measurements, our tested roundup of locks for French doors pairs real hardware with the door types it fits.

Installation Order And The Mistakes That Cost You

Install the active lock first, verify alignment before final tightening, and test with the door open — forcing the leaves closed is how hardware gets damaged.

1. Decide which leaf takes the active lock, then install a dummy or matching handle on the inactive leaf where required.
2. Install or verify the inactive leaf’s top and bottom bolts.
3. Align the strike, then tighten everything down.
4. Test operation with the door open. For multipoint systems, lift the handle to engage the deadbolts, then turn the key toward the slave door to engage the main deadbolt.

Multipoint instructions also call for adjusting hinges if needed, aligning the keep with the lock groove, and retesting after securing the keep. Mortise installs require marking and drilling from both sides, seating the lockcase and faceplate flush, confirming spindle and key operation, then transferring latch and deadbolt positions to the frame before cutting striker apertures.

The most common mistakes: putting a smart lock on the inactive leaf (which has no latch and strike), ordering left- or right-handed handles incorrectly — Schlage advises selecting both left- and right-handed levers where paired doors require them — and bolting a standard deadbolt onto a multipoint or mortise door without confirming lock-body compatibility. Forcing the doors together when a multipoint won’t engage is the same error in a different outfit.