Keep your windows securely closed and safe with these U 9809 Sliding Window Locks for Vinyl Windows. The locks feature an adjustable jaw that has a “vise-like” grip, and they are capable of opening up to ½” wide. Use them to prevent unwanted intruders from breaking into windows or to prevent accidental falls. These locks are designed for use on horizontal vinyl sliding windows, although they may also work with some vertical sliding (single hung) windows. Installation is quick and easy with no tools required – a more secure window is just minutes away! When installing this lock, the cam style locking lever should be rotated hand-tight over the rail or vinyl edge to a sufficient torque prior to locking down the lever. This lock can be adjusted to fit on rail thicknesses ranging from 1/16 in. to 1/2 in. thick. This sliding window lock can be used as a secondary lock when window is shut and to secure the windows during ventilation. For a larger version of this lock (used on vinyl frame patio sliding doors) see model number U 10547.