Stop Windows From Being Opened: 7 Ways

This guide covers practical ways to stop house windows from being opened, whether you’re dealing with child safety, security concerns, or a stuck-open window that won’t stay shut. You’ll learn permanent and temporary solutions that work on most common window types, from simple pins to locking mechanisms.

What You’ll Need

Window locking pins or keyed window locks (available at hardware stores)
Drill with appropriate drill bits (for pin installation)
Measuring tape
Pencil or marker
Wood screws or machine screws (matching your window frame material)
Screwdriver (manual or power)
Window wedge or sash stopper (for temporary solutions)
Optional: child safety window guards or grilles

Step-by-Step

Identify your window type. The method you use depends on whether you have double-hung windows (slide up and down), casement windows (crank outward), sliding windows (slide left or right), or awning windows (hinged at the top). Check the manufacturer’s label on the window frame if available.
Choose your stopping method. For a permanent solution that allows you to still open the window when needed, install keyed window locks. For a temporary fix, use window wedges or sash stoppers. For childproofing, consider window guards or stops that limit how far a window can open.
For double-hung windows (most common): Close the window completely. Measure and mark a spot on the upper sash (the top part of the window) about 1 inch above the lower sash’s top edge. Drill a pilot hole at this mark, angled slightly downward. Insert a window locking pin through the upper sash into the lower sash track. Test that the pin prevents the window from sliding up.
For sliding windows: Close the window fully. Place a wooden dowel or a commercially available sliding window lock in the bottom track. The dowel should be cut to fit snugly between the sash and the opposite end of the track. For a more secure option, install a keyed sliding window lock that screws into the track.
For casement windows: These windows crank outward, so the locking point is on the crank mechanism. Most casement windows have a built-in lock on the handle. If yours doesn’t, install a casement window lock that attaches to the frame and the sash, preventing the crank from turning. Alternatively, remove the crank handle when the window is closed and store it separately.
For child safety: Install window stops that limit how far the window can open. These are small brackets that attach to the window track and physically block the sash from moving beyond a certain point. Many building codes require windows to open at least 4 inches for emergency escape, so check your local regulations before installing stops that fully prevent opening.
For security against break-ins: Install keyed window locks on all ground-floor windows. These locks use a key to lock and unlock, making it impossible to open the window from the outside even if the glass is broken. Position them at both the top and bottom of double-hung windows for maximum security.
Test your solution. After installing any locking device, try to open the window from both inside and outside. Ensure the lock engages properly and the window cannot be forced open without significant effort. If you installed a pin, verify it doesn’t interfere with normal operation when removed.
For a temporary solution: If you need to stop a window from being opened immediately without tools, use a wooden wedge or a thick rubber stopper. Insert it between the sash and the frame on the side opposite the latch. This works best on windows that slide vertically or horizontally.

Common Mistakes

Drilling without measuring: Installing a pin or lock at the wrong height can prevent the window from closing fully or leave a gap that lets in drafts and rain.
Using the wrong screw length: Screws that are too long can penetrate the window frame and damage the glass or the wall. Screws that are too short won’t hold the lock securely.
Blocking the emergency exit: Making a window impossible to open can be a fire hazard. Always ensure at least one window in each bedroom can be opened from the inside without tools, and consider whether your solution allows for emergency escape.
Ignoring the window’s condition: If the window is already difficult to open or close due to warping or broken hardware, adding a lock won’t fix the underlying problem and may make it worse.
Forgetting about the upper sash: On double-hung windows, locking only the lower sash leaves the upper sash unsecured. An intruder can push the upper sash down to gain access.

Tips

For rental properties, use non-damaging solutions like window wedges or removable track locks. These don’t require drilling and can be removed when you move out.
Consider a window alarm in addition to a physical lock. Alarms deter opening and alert you if someone tries, but they don’t prevent opening by themselves.
If you have multiple windows that need securing, buy locks in bulk from a hardware store—they’re often cheaper per unit.
Clean and lubricate the window tracks before installing any lock. A smooth-operating window is easier to secure properly.
For sliding windows, a simple wooden dowel cut to length is surprisingly effective and costs almost nothing. Paint it to match the frame for a cleaner look.
If you have young children, combine window stops with a latch that’s out of reach. Place the stop high enough that a child can’t unlock it, but low enough that an adult can reach it easily.

Troubleshooting

The window still opens despite the lock: Check that the lock is properly aligned with the strike plate or track. If using a pin, verify it’s long enough to engage both the sash and the frame. You may need a longer pin or a second locking point.
The lock won’t engage: This usually means the window isn’t fully closed or the frame is warped. Try adjusting the window’s position slightly. If the frame is warped, you may need to sand down the high spots or install a shim behind the lock.
The window won’t close after installing a lock: The lock or pin may be protruding too far into the track. Remove it, sand down the back, and reinstall. Alternatively, the screw may be too long and hitting the frame—replace with shorter screws.
The key is lost for a keyed lock: Most keyed window locks come with two keys. If you lose both, you’ll need to drill out the lock cylinder and replace the entire lock. Keep spare keys in a known location, like a kitchen drawer.
The window is stuck open and won’t close: This is the reverse problem. If the window is stuck open, don’t force it—you may break the glass or frame. Check for debris in the track, then apply lubricant. If it’s still stuck, the sash may have come off its track; gently lift it back into place.
Condensation or drafts around the lock: The lock installation may have created a gap. Apply weatherstripping around the lock area or use a silicone sealant to fill gaps. This also improves insulation.

Frequently Asked Questions

Q: Can I stop a window from being opened without drilling holes?
A: Yes. Use window wedges, track locks that clamp onto the frame, or a wooden dowel in the track. These are non-damaging and removable.

Q: What’s the best way to childproof a window?
A: Install window stops that limit opening to 4 inches or less, and place the latch out of a child’s reach. Combine with a window guard if the window is above the first floor.

Q: Will a window lock prevent a burglar from breaking the glass and opening the window?
A: A keyed lock prevents the window from being opened even if the glass is broken, because the lock mechanism is separate from the glass. However, a determined burglar could still break through the frame—no lock is 100% foolproof.

Q: How do I stop a window from being opened from the outside?
A: Use keyed locks on all operable windows. For double-hung windows, lock both the upper and lower sashes. Consider adding security film to the glass to make it harder to break.

Q: Is it legal to prevent a window from opening?
A: In most areas, you must maintain at least one emergency escape window per bedroom. Check your local building codes before installing locks that fully prevent opening. Window stops that allow partial opening are usually compliant.

Q: Can I stop a window from being opened if it’s already broken?
A: If the window is broken and won’t stay closed, you can temporarily board it up or use a wedge to hold it shut. For a permanent fix, the window hardware or the window itself needs repair or replacement.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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