Defender Security U 9920 Security Bar For Sliding Patio Doors, Adjustable, Aluminum Construction With Aluminum Finish, Pack of 1 Easy to install and provides backup security for your sliding patio door Adjustable to accommodate openings from 28 in. to 48 in. The adjustable feature allows you to safely enjoy fresh air by securing your door in an open position This item works on almost all sliding glass doors whether the sliding panel is in front of the stationary panel or behind the stationary panel (refer to Prime-Line's How-To video for instructions on how to install) Can be used on metal, vinyl or wood sliding patio doors or windows