On each end of the aluminum support you have to make a cut out. This is so the support will clear the wide roof supports in the coach. One end will be shorter then the other. make sure you have enough clearance because once it\'s fiberglassed down it will be difficult to make any adjustment. The aluminum can be cut with a tin snips. It can be malleted down and use a grinder to finish it. In other words your going to have to fabricate these ribs. Take your time and do it right.