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Window Won't Lock Because the Sash Is Out of Alignment

When the lock cam doesn't reach the keeper, your window sash shifted. Fix the alignment in 15 minutes — no new parts, just a screwdriver and a block of wood.

Category:Doors & Windows

Difficulty:Easy

Time:15 min

Success:50%

Updated:May 22, 2026

quick_referenceQuick Answer

For Window Won't Lock Because the Sash Is Out of Alignment, start with "Clean the sash track and check for obstructions": Open the window and run your finger along the bottom track and the side channels where the sash slides. Remove any paint chips, debris, or bug carcasses with a vacuum and a putty knife. Close the window again — slowly — and watch whether the top sash is fully seated in the header channel. A 1/16-inch gap at the top is enough to misalign the lock. If you find hardened paint drips on the track, scrape them flat with a razor scraper. Stop DIY if the window frame is rotted, cracked, or separating from the rough opening — the entire window unit may need replacement. forcing a lock on a failed frame can shatter the glass. This is listed as a easy recovery and usually takes about 15 min.

verifiedGuide Snapshot

Repair areaDoors & Windows

Estimated time15 min

DifficultyEasy

Stop conditions4

Last updated May 22, 2026. Review the stop conditions before continuing.

account_treeRecovery State

DeviceWindow

Current stateWont Lock

Specific stateSash Misaligned

Failed stepWindow Lock Engagement

Likely failure typeMisalignment

DIY boundaryDIY recovery first

paymentsCost decision

help1. Understand the Problem

Double-hung and sliding windows rely on the lock cam on one sash to engage a keeper plate on the other. Over time, the sash settles, the frame shifts with seasonal humidity, or the lock itself loosens. The cam misses the keeper by 1/8 inch and the window won't lock. Sometimes it's a paint drip blocking the sash from fully closing. Less commonly, the balance mechanism inside the jamb is worn and the sash sits tilted.

build_circle2. Try This First

Best First Step

Clean the sash track and check for obstructions

Open the window and run your finger along the bottom track and the side channels where the sash slides. Remove any paint chips, debris, or bug carcasses with a vacuum and a putty knife. Close the window again — slowly — and watch whether the top sash is fully seated in the header channel. A 1/16-inch gap at the top is enough to misalign the lock. If you find hardened paint drips on the track, scrape them flat with a razor scraper.

visibility3. Visual Guidance

See what's happening and how to try the first recovery step.

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Check the lock alignment with the sash closedClose and latch the window as far as it goes. Look at the gap between the cam on the bottom sash and the keeper on the top sash. If the cam is too high, too low, or offset left-right by more than 1/16 inch, mark the offset with a pencil. On vinyl windows, the keeper slot is often adjustable — look for slotted screw holes.

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Adjust the keeper plate positionUnscrew the keeper plate from the top sash — two screws, usually Phillips #2. The screw holes in the keeper are slotted to allow up to 1/8 inch of vertical adjustment. Slide the keeper to your pencil mark, tighten the screws, and test the lock. If you need more travel than the slots allow, drill new screw holes and fill the old ones with toothpicks and wood glue.

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Shim the sash if the frame itself shiftedIf adjusting the keeper doesn't get you there, the lower sash isn't sitting square. Open the window, place a small wood shim or folded cardboard under the low corner of the sash, and close it. The shim lifts the corner just enough to realign the cam with the keeper. This is a temporary fix — if the frame is that far out of square, the window may need reinstallation.

autorenew4. If That Doesn't Work

Try the next recovery options.

lock

Replace the lock assemblyIf the cam lobe is worn rounded or the keeper slot is wallowed out from years of forcing, a new sash lock is $5-10. Two screws, no modifications needed. Match the hole spacing — most are standard 2-1/4 inch center-to-center.

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balance

Check the window balance mechanismIf one side of the sash sits lower than the other and won't stay up, the spiral balance or block-and-tackle balance in that jamb is broken. Remove the sash, disconnect the balance from the jamb channel, and take it to a window supply shop to match.

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add_circle

Add a secondary surface-mount lockIf the original lock is completely toast and you need security now, a surface-mount sash lock installs in 5 minutes with 4 screws above the old lock. They're ugly but they work on any window.

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Frequently Asked Questions

My window locks fine in summer but not in winter. Why?expand_more

Seasonal expansion and contraction. In winter, the vinyl or wood frame shrinks slightly with cold and low humidity, pulling the lock surfaces apart. In summer it swells back. Adjust the keeper to the winter position — it'll still work in summer, just be slightly tighter.

Can I use WD-40 to free up a stuck window lock?expand_more

WD-40 attracts dust and turns gummy over time. Use a dry graphite lubricant or a silicone spray instead. Work the lock back and forth 10-15 times to distribute the lubricant into the mechanism.

The lock handle turns but the cam doesn't move. Is it broken?expand_more

The cam is held onto the lock spindle by a small set screw that often loosens over time. Remove the two mounting screws, lift the lock housing, and tighten the set screw on the underside with a small flathead driver.

warning5. Stop DIY If

Don't continue if any of these apply.

reportThe window frame is rotted, cracked, or separating from the rough opening — the entire window unit may need replacement. Forcing a lock on a failed frame can shatter the glass.

reportYou see condensation between double-pane glass or the glass itself is cracked — the seal has failed. Lock issues are secondary to a failed insulated glass unit.

reportThe sash is physically jammed and won't budge even with the lock removed — the frame may be racked from foundation settling. Forcing it can crack the glass or pop the frame apart.

reportYou're dealing with a second-story window and can't safely access the exterior side of the sash for adjustment — working at height with both hands occupied is asking for a fall.

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