Designed with 20-gauge steel to improve security on hinged and sliding doors the Guard Dog Door Keeper prevents forceful entry of even the largest intruders. The adjustable system allows the door bar to slide to fit most standard-sized doors. Want to use it on a sliding door? Simply remove the top yolk pin and the Door Keeper is ready for action. Whether at home, school, or the office, the Door Keeper keeps what you want out.