The essentials in 30 seconds
A sliding glass door usually has a main lock (a mortise hook latch inside the edge of the door, worked by the handle) and can take one or more secondary locks. To lock and unlock from outside, you need an exterior keyed handle set or a key cylinder that suits it. Secondary locks include a security bar across the track, a foot lock pressed down into the track, a twist-in pin lock that stops the panel sliding and lifting, a loop lock that can be mounted high, out of children's reach, and a stick-on lock for the glass. Mortise latches are not universal: measure the mounting hole spacing and compare it with the old part before buying.
- Many secondary locks also hold the door partly open for ventilation.
- Keyed locks that lock from both sides need the key close at hand to get out.
- Read the manufacturer's line drawing or dimensions before buying.
Sliding glass door lock types
| Type | Where it goes | What it does |
|---|---|---|
| Mortise hook latch | Inside the edge of the sliding panel, worked by the handle | Main lock: a spring-loaded hook latches the door closed |
| Exterior keyed handle / key cylinder | Handle set on the outside | Locks and unlocks from outside with a key, plus a thumb lock inside |
| Security bar | Across the track, between the panel and the frame | Stops the door being forced open; adjustable models fit 28 to 48 in. openings |
| Foot lock | In the track, pressed down with your foot | Holds the door closed or partly open |
| Twist-in pin lock | Lower back edge of the sliding panel, bolt into the fixed panel's rail | Prevents sliding and lifting of the active panel |
| Push-in keyed lock | On the door, with a steel bolt | Keyed secondary lock; helps prevent prying and lifting |
| Loop lock | Door jamb and door | Secondary lock; can be fitted high, out of small children's reach |
| Stick-on glass lock | Glass of the fixed panel, self-adhesive | Blocks the door closed or open for ventilation, no tools needed |
Mortise sliding glass door locks
The lock inside most patio door handles is a mortise lock: a lock body set into the edge of the sliding panel, with a spring-loaded hook latch. Prime-Line describes one of its replacement models (E 2014) as having an adjustable hook latch, a 45-degree keyway for surface-mounted handle sets and 3-11/16 in. mounting hole spacing, and asks buyers to verify the dimensions for a proper fit. In other words, a mortise lock is not a universal part:
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01
Remove and keep the old lock
Take it with you, or photograph it next to a tape measure.
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02
Hole spacing
Measure between the mounting holes and match it exactly.
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03
Faceplate
Match its shape: the E 2014, for example, has a round faceplate.
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04
Handle and keyway
The lock must suit your handle set and, if keyed, its keyway angle (vertical or 45 degrees).
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05
Door material
Check the lock is listed for your door (wood, aluminium or vinyl).
Sliding glass door locks with a key
- Exterior keyed lock: Andersen offers exterior keyed locks on its sliding doors that let you lock and unlock from the outside, with an interior thumb lock.
- Key cylinder: Prime-Line's sliding glass door key cylinder fits most surface-mounted patio door handle sets, works with vertical and 45-degree keyways and can be bought keyed alike.
- Push-in keyed lock: a secondary lock with a steel bolt that Prime-Line says helps prevent prying and lifting of the active panel and unwanted opening from either side.
Security bars, foot locks and pin locks
A secondary lock adds a second barrier without replacing the main lock.
- Security bar: Prime-Line's adjustable bar telescopes to fit openings from 28 to 48 in. without cutting, can hold the door open for fresh air and swings up out of the way when not in use.
- Foot lock: Andersen's auxiliary foot lock sits in the track and is pressed with your foot; it works with the door closed or partly open, and Andersen describes it as an upgrade on a dowel in the track.
- Twist-in pin lock: mounts on the lower back edge of the sliding panel; its bolt goes into a 1/4 in. hole drilled in the fixed panel's bottom rail, so it stops the panel sliding and lifting. Prime-Line says it also suits some horizontal sliding windows.
- Track lock with thumbscrews: clamps onto the track; Prime-Line warns not to over-tighten it and damage the track.
Childproof sliding glass door locks
For small children, the point is a lock they cannot reach or work. Prime-Line says its loop lock gives an added level of child safety because it can be installed higher on the door, out of reach, to prevent unsupervised access outside. A stick-on lock on the fixed glass is another option that needs no tools. Whatever you choose, adults must still be able to open the door quickly.
What about the glass itself?
A lock only secures the panel. Andersen says all its patio doors use tempered glass. For other doors, check the glass type with the maker; to make glass harder to see through or add a film layer, see window film.
Sliding glass door locks: frequently asked questions
What types of sliding glass door locks are there?
The main mortise hook latch in the handle, exterior keyed locks and key cylinders, and secondary locks such as security bars, foot locks, twist-in pin locks, push-in keyed locks, loop locks and stick-on glass locks.
Are sliding glass door mortise locks universal?
No. Measure the mounting hole spacing, faceplate and keyway and compare them with the old lock before buying.
Can I lock a sliding glass door from the outside?
Yes, with an exterior keyed handle set or a key cylinder that fits your handle set.
What is the best extra lock for a sliding glass door?
It depends on the goal: a security bar or foot lock to block the track, a pin lock against sliding and lifting, or a high loop lock for child safety.
How do I childproof a sliding glass door?
Fit a secondary lock out of children's reach, such as a loop lock mounted high on the door, and make sure adults can still open it quickly.
Can I keep a sliding door locked while it is partly open?
Some secondary locks allow it: foot locks, adjustable security bars, thumbscrew track locks and stick-on glass locks can hold the door in a ventilating position.
Sources
Door and hardware manufacturer information, checked on 2 November 2026 (02/11/2026).
- Andersen · Sliding patio doors ↗Auxiliary foot lock in the track, used closed or partly open, upgrade on a dowel; exterior keyed locks with interior thumb lock; tempered glass on all patio doors.
- Prime-Line · E 2014 mortise lock for sliding patio doors ↗Spring-loaded hook latch; wood, aluminium and vinyl doors; 45-degree keyway for surface-mounted handle sets; 3-11/16 in. hole spacing; verify dimensions.
- Prime-Line · Sliding patio door security ↗Range of secondary locks: twist-in lock, adjustable security bar, key cylinder, double thumbscrew lock, stick-on glass lock, loop locks, push-in keyed locks. Read in the browser.
- Prime-Line · Twist-in patio door lock U 9848-L ↗Prevents sliding and lifting; mounts on the lower back edge; 1/4 in. hole carefully drilled in the fixed panel's rail; also some sliding windows. Read in the browser.
- Prime-Line · Adjustable security bar U 9921-L ↗Telescopic 28 to 48 in.; no cutting; holds the door open; swings up when not in use. Read in the browser.
- Prime-Line · Sliding door loop lock S 4378 ↗Secondary lock on jamb and door; child safety by mounting higher on the door. Read in the browser.
- Prime-Line · Push-in sliding door keyed lock S 4005 ↗Keyed from either side; steel bolt; helps prevent prying and lifting. Read in the browser.
- Prime-Line · Sliding glass door key cylinder ↗Fits most surface-mounted patio door handle sets; vertical and 45-degree keyways; keyed alike. Read in the browser.
- Prime-Line · Double thumbscrew sliding door lock U 9805-L ↗Closed or ventilating position; do not over-tighten on the track. Read in the browser.
- Prime-Line · Glass surface patio door lock U 9842-L ↗Self-adhesive on the stationary glass; closed or ventilating position; no tools. Read in the browser.
Track full of grit?
Clean it before fitting a track lock or bar, and call a door specialist if the frame is damaged.