The door system disclosed herein includes a frame and a door fabricated from a plurality of horizontal and vertical wire rods. The door may have an inverted hook which is aligned to a horizontal wire rod of the frame when the door is pivoted to the closed position. To close the door, the door is dropped so that the horizontal wire rod of the frame is traversed into the inverted hook. At this point, the animal inside of the pet crate cannot open the door by pushing on the door. Rather, the door must be raised so that the inverted hook clears the horizontal wire rod of the frame to pivot the door to the opened position.