A pet apparatus that facilitates the movement of a household pet through a pet door opening provided in a door at the head of a stairway leading to a lower level of a building. The invention comprises a rigid platform member engaged with a barrier member, and a support member that is attached to the stairway door to safely redirect the pet to travel in a left or right direction, relative to the pet door opening, to prevent the pet from falling down the stairway. A collapsible embodiment of the invention incorporates foldability. Additional embodiments to the collapsible embodiment include manual, cord, and spring-operated foldability. The device is intended for use in combination with commonly available pet doors.