What I did was slowly bend the cardboard over about weeks time. I have some photos in my photobucket some place. I started on a Sunday evening and by the next weekend I had it formed pretty close and could get it in place. I slightly over bent it figguring it would have some spring back. I did not use water. I trimmed the edges along the doors after it was scerwed in place. I worked from the center out. Measured and drilled the first few center holes working from a center line and then just used an awl.