Keeping would-be intruders outside is an important concern for most homeowners. Though hinged doors are relatively easy to protect with proper latches and deadbolts, windows and sliding glass doors are not as simple to secure. Windows and doors that slide can be forced open or lifted off their tracks, and glazing can be broken.

In addition to installing locking devices, you can enhance security by replacing all ordinary glass with tempered, laminated, or wire-reinforced glass or with plastic, as well as by installing perimeter alarm systems.

Several ready-made devices are available to make prying open a window and/or removing a sliding glass door from its track more difficult. The right locking device to choose will depend on whether you need to secure a sliding window or door, or a double-hung window.

To keep a panel from sliding, use track grips, tightened by a thumbscrew or key, or metal stops that straddle the lower track and are secured with a lever or thumbscrew that clamps them in place. Or use a spring bolt, which is screwed to the sill or base track and has a pin that snaps through a hole drilled into the edge of the lower track and bottom of the sash.

Even more secure is a bar that screws to the doorjamb and swings up into a saddle on the edge of the door to lock it in place; an advantage of this type of bar is that it can be adjusted to allow the door to be partially open.The easiest way to keep an inside panel from sliding is to drop a dowel or a piece of tubing into the empty portion of the lower track. Cut it 1/4 inch shorter than the distance between the panel and the jamb.

Double-hung windows can be locked with wedge locks, key-operated latches, or locking pins that go through one sash and into the next.