Each side has a vent hole in the door jamb.  Mine had rusted bottoms from the junk thrown into the fender-wells from the rotating tires.  I used a bent copper pipe and some pennies to hold metal scraps and then welded into that.  A round grinding ball was mounted to my drill and I ground-down the welds.

 

 

 

Everything inside the fender well was sanded, caulk stripped out of the sail panel seams, undercoat was injected into the sail panel seams and then it was epoxy coated red.