I was really happy with our last whelping box and have been asked by a couple folks so here are pics of it.
The box is made of 3 ft high pvc hog farrowing panels with extruded slot corners. It measures 5 ft by 4ft with a latching door cut out of one of the long sides. The pig rails are made of pvc piping. The entire thing is extremely lightweight and easy to clean. Very durable and easy to take apart and store.