Window Won’t Lock Closed? Check Sash Alignment Before Forcing the Latch

Test the lock with the window open before you move any hardware

With the sash safely supported and the window open, operate the lock gently. If the handle moves normally when open but binds only when the sash is closed, the lock mechanism may be fine and the sash-to-frame alignment is the better place to look. Andersen troubleshooting guidance uses this same distinction when separating lock hardware problems from sash alignment problems on specific window types.

If the lock is stiff even with the window open, stop forcing it. Loose screws, damaged hardware, corrosion, or an internal multipoint mechanism can be the issue. Use the window brand and model instructions because casement, sliding, single-hung, and double-hung locks adjust differently.

Make sure the sash is actually all the way home

On double-hung windows, press the upper sash fully upward and the lower sash fully downward before trying the lock. A sash that has slipped slightly after tilting for cleaning can leave the meeting rails too far apart for the lock to engage. On sliding windows, debris in the sill or track can keep the panel from reaching its fully closed position.

Vacuum loose dirt and wipe the manufacturer-approved track surfaces. Avoid oily lubricants unless the window maker recommends them; some manufacturers warn that oily products attract dust and make operation worse. Do not plane, file, or cut a vinyl or composite sash just because it feels tight.

1. Open the window and confirm the lock operates freely without the sash in the way.
2. Clean dirt, paint chips, insects, and debris from the sill, track, and meeting surfaces.
3. Close each sash or panel fully and compare the gap around the frame for obvious crookedness.
4. Tighten only clearly loose accessible hardware using the manufacturer's guidance; do not relocate the keeper by guesswork.
5. Retest without forcing the handle.

A crooked reveal is a clue that the lock is not the real problem

The narrow gap between a sash and frame is often called the reveal. Andersen's service guidance for some casement and gliding windows uses an uneven reveal as a sign that the sash may need model-specific adjustment. If the gap is tighter at one corner and wider at another, moving the lock keeper alone can hide an alignment problem and may reduce weather sealing.

Window adjustments can involve balances, glides, hinges, or operator hardware and are not universal. Use the exact manufacturer's service instructions or have a window technician make the adjustment, especially on a large or heavy sash. Renters should document the misalignment and request maintenance instead of drilling new keeper holes into the frame.

Do not trade security for emergency escape

A lock that will not engage matters for security, weather sealing, and child safety, but a repair should not permanently block a window that is intended for emergency egress. CPSC recommends window guards and stops for child-fall prevention while also emphasizing that certain guards must be releasable for escape depending on the location and jurisdiction.

Never rely on an insect screen to prevent a fall. If the window cannot be secured overnight, use a manufacturer-compatible temporary security measure only if it does not violate an egress requirement, rental rule, or fire-safety function.

Replace the right part only after you know what is misaligned

For a replacement lock or keeper, match the window manufacturer, series, sash material, screw spacing, handing where applicable, and finish. A generic latch with similar dimensions can interfere with the weatherstrip or pull the sash out of position if its geometry is different.

If the frame is visibly bowed, water-damaged, rotted, cracked, or out of square, or if the sash is heavy and sagging, the lock is not the main repair. Those conditions deserve window or building-envelope service before the hardware is forced into alignment.