How to Make All Types of Window Locks More Secure

Don't forget your home's windows when it comes to safety. We'll walk you through lock options, the installation process, and more.

white home exterior
Photo: William Geddes 

Window "shopping" is a favorite pastime for burglars. Inadequately protected windows are easy marks for thieves, who have an arsenal of tricks for the quickest, easiest ways to force them open. Fortunately, safeguarding your home's windows is neither difficult nor expensive.

Start with a quick survey of your windows—including in the basement and garage and second-story windows that would be easy to reach from the ground. Next, make a list of the windows, noting their type—such as double-hung or casement—and the kind of lock each has.

You'll probably need to replace or at least augment the locks on most of them. Keep fire safety in mind as you consider new locks and fastening devices. For example, if you install keyed locks, you'll want to keep keys nearby. Everyone in your family needs to know where they are in case of an emergency.

If you've identified a few especially vulnerable windows, you may feel that even sturdy locks aren't sufficient protection. In that case, consider replacing the standard glazing with impact-resistant acrylic or polycarbonate or with high-security glass. Or, where appearance isn't of prime importance, install a metal grille outside the window or a scissors-type security gate inside. Be aware that although some gates have quick-release levers for emergency exits, a stationary grille will render the window useless as an exit in the event of a fire. Another choice is a phone-in security system that notifies the police or paid security company when one of the sensors placed on windows and doors detects an intrusion.

Types of Window Sashes

window with bright sash
Adam Albright

Burglars usually try to enter through a door first and then a window. A thief typically wants to avoid making the noise created by breaking glass. Thus, the higher quality of the sash, the more protection it offers.

The ordinary sash latches that act as double-hung window locks may help squeeze out drafts, but they offer little protection against break-ins. An intruder can insert a knife up between the sash and flip the latch open, or if he's in a hurry, force the lower sash and snap the latch off with little effort.

With a good-quality lock installed and fastened, the intruder must break a hole in the glass to reach a lock that he can turn to open the window. If you want to occasionally keep the window partially open for ventilation, install a wedge lock or bore several holes for a bolt-type lock. If a keyed sash lock is installed, the intruder must break all the glass and crawl through the sash.

Locks for Double-Hung Sashes Hinged Wedge Lock

hinged wedge lock
Dave Toht

A hinged wedge lock allows you to open a window partially but prevents the sash from lifting far enough to allow an intruder to enter. Swing it away, and you can open the window to any height.

Folding Lock

folding lock
Dave Toht

A folding lock for a double-hung window can be unlocked and folded to one side so the sash can be raised.

Keyed Sash Lock

keyed lock for sliding window
Dave Toht

Keyed sash locks are available to fit most double-hung windows. Simply remove the old lock, fill the screw holes, drill new fastener holes, and install the unit.

How to Install a Casement Window

casement window in dark kitchen
Brie Williams 

Casement windows are one of the most secure types you can own. A strong casement in good condition may not need a lock at all. If the window is large enough for an adult to get through (and it opens to more than 6-1/2 inches), simply consider removing the operator crank and keeping it well out of window reach.

If the sash wobbles when you operate the crank, needs to be propped open, or rattles in a high wind, install a chain lock (the same type used on doors) to keep the window from opening too much. For maximum security, fasten it to the sash and frame with the longest screws that the window will accommodate.

Install a chain lock (the same type used on doors) to limit the distance the window will open. Then, for maximum security, fasten it to the sash and frame with the longest screws that the window will accommodate.

For additional protection, install a keyed lock along the sash rail. Be sure to keep the key in a nearby location where all family members can find it in the event of an emergency exit.

4 Ways to Secure a Sliding Window

sliding window over farmhouse sink
Kritsada Panichgul

Drive Screws into Tracks: To keep window sashes securely in their tracks, drive sheet-metal screws partway into the upper tracks. Adjust the screws, so the window barely clears them as it slides, with no wiggle room for maneuvering the sash up over the lower tracks.

Install a Metal Clip: A simple metal clip will prevent a burglar from prying open the sash by snapping the brittle metal catch that holds the window closed. Bend the clip to fit your window channel, and install it in the lower track wedged against the closed inner sash.

Add a Bar: Although more conspicuous, a Charley bar also will stop an intruder from prying open a sliding window. When you don't need protection, simply raise it to its "up" position and clip it against the inner sash.

Install Locks: Key-operated locks are perhaps the most secure way to protect sliding windows. They'll work with vertical sliding windows, too. Mark the lock's position on the windowsill with the sash fully closed, and drill a bolt hole in the sill at that location. To secure the window in partially open positions, simply drill additional holes in the sill.

Locks for Sliding Windows Keyed Locks

keyed lock for sliding window
Dave Toht

Keyed locks for sliding windows are available in several styles. This type needs no permanent fastening; it simply clips in place before locking.

Screw-Type Locks

screw-type locks for sliding window
Dave Toht

This inexpensive screw-type lock will secure a sliding window. You simply slip it over the lip of the track, push it against the window, and screw it tight onto the track.


dowel rod
Dave Toht

If you want to be able to open a sliding window, the simplest security measure is a 1-inch dowel cut to fit between the sliding window and the jamb. Lay it flat in the track to secure the window.

4 Ways to Secure Basement Windows

family room in basement
Kim Cornelison

Drive Long Screws: If your basement windows don't have locks, drive long screws into the stop on each side at a height that will let you open the window only a few inches. (Because the screws would be hard to remove in a hurry, reserve this solution for windows you won't rely on for exit in an emergency.)

Add a Sliding-Bolt Lock: A keyed sliding-bolt lock (or a sturdy hasp fitted with a keyed padlock) offers more security and the ability to quickly exit in an emergency. Keep the key nearby but beyond the reach of someone outside the window.

Install a Keyed Gate: If you're concerned about an intruder breaking the glass to gain access but still want the window for an emergency exit, install a scissors-type gate secured with a keyed padlock. Again, keep the key handy and easy for family members to find.

Add a Grill: Standard or custom-made grilles permanently mortared into the outside foundation will provide maximum security in high-crime areas, although at the expense of giving your windows a behind-bars look. As with glass block, these will render the windows useless as emergency exits in the event of a fire.

4 Ways to Install Key-Operated Security

window over bathtub
James R. Salomon

Drill into the Sash: Key-operated lag screws are available in kits at most hardware stores. Predrill the sash, and insert the screws through their recessed washers. Tighten the screws with the key provided. Drilling additional holes in the upper sash will let you keep the window locked in a partially open position for ventilation.

Wedge Lower Sash: Easier still is wedging the lower sash in its fully closed position with a length of scrap wood. Cut the strip to the exact size, fit it into the channel that operates the lower sash, and tack it in place. This solution is best for windows you don't open often. However, it's not as tidy-looking as lag-screw locks and won't let you secure the window in a partially open position.

Replace Sash Latch: If you'd rather not drill extra holes in your sash but want the protection of a keyed lock, you can replace the sash latch with a key-operated lever. Be sure to keep the key near enough for a quick emergency exit but out of reach of a prowler's exploring hand.

Install a Bolt-Action Lock: A keyed bolt-action lock lets you lock the window in various open positions—just install additional brackets on the upper sash.

How to Install Security Bars

installing security bars over windows
Dave Toht

Security bars come in various sizes, each of which is adjustable to suit almost any window. Many come with locking mechanisms that permit you to swing the security bars open. They mount on the casing or, for deep-set windows, to the jamb. In each case, the fasteners must penetrate to the framing members.

Typically, mounting hardware is provided, often with anchors needed for masonry walls. Center one bracket for the mounting hardware, plumb, drill pilot holes, and attach the fasteners. Use the bars for positioning the opposite bracket. Mounting screws often come with inserts that make the screws difficult to remove.

Ultimate Security Option: Glass Block

glass block
Dave Toht

Where security is of more concern than seeing the vista outdoors, consider glass block. Prefab units can be ordered that spare you the fuss of mortaring together separate blocks.

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