I never needed to. Once it was in, it never moved. When I was scribing the shape, I measured the bulk head 2mm smaller than the space it sits in. Then added a soft 5mm gasket so it can compress against the sides and roof of the van. Snug fit. I had to cut some extra bits off the side to allow for the seat belts in the back but it serves me very well. No damage or brackets added to the sides.