This window flip lock is constructed of stamped steel and comes in an antique brass finish. Features a simple to install, and simple to operate design for use on vertical sliding (single and double hung) wood windows. Upon mounting this lock on the stile face, towards the bottom of the upper sash, it creates a wedge between the top and bottom sash preventing the bottom sash to be lifted. The hinged wedge design can be swung opened to allow for opening of lower sash. Designed for use on single glazed/single pane vertical sliding wood windows for ventilation, or secondary locking purposes. Warning! To avoid glass breaking, on narrow sash frames, measure the vertical window sash from glass edge. IF LESS THAN 3/4 INCH THICK, CUT THE NAILS TO 5/16 INCH LONG BEFORE INSTALLING. NOT RECOMMENDED FOR DUAL PANE WINDOWS.