Designed with 20-gauge steel to improve security on hinged and sliding doors the DoorKeeper 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 on a sliding door? Simply remove the top yolk pin and DoorKeeper is ready for action. Whether at home, school or the office. The DoorKeeper is also recommended for use with the Pop Up Pet Door for extra support.