18" WinLock is a window security lock that prevents burglars from breaking into your home by isolating the window to prevent raising or lowering of either window pane by securing it from the inside and outside. WinLock provides single and double hung protection that is ideal for those who use air conditioners, fans, ventilation systems, etc that leaves your window open and unable to latch. It also can be used on a completely closed window to provide added protect against a intrusion.