Abstract: A moulded plastics pet door for relatively large animals comprising a rectangular frame for attachment to the sides of an aperture in a main door, a second U shaped frame engaging a frame on the rectangular frame and a flap engaging a frame on the second frame both the frame and the flap being pivoted on a rod extending transversely of the rectangular frame, shielded magnets being provided on the second frame and the flap to engage shielded keepers on the second frame and the flap. The flap is moulded with hollow reinforcing ribs and with slots in the rear side to receive bolts for locking the second frame and flap to the rectangular frame to prevent use of the pet door.