the bolt goes through a 1/4 inch aluminum plate (part of the mast base) through about 1 inch of deck (where the bolt broke) to the backing plate which is maybe a 3/16 plate of aluminum(although I suspect slightly less). Problem is you can't get to the backing plate without cutting an access port in the plastic which is the headliner in the head. I haven't cared too much since the consensus is that the sheer amount of compression and the existing 5 bolts are enough to prevent movement.