I made these parts a long time ago for my roadster. The channels are quarter panel braces for upholstery support. They were copied from originals.. I made hammer forms from the originals and the forms fit the originals. They attach to the sides of the foot recess under the seat and under the quarter panel. I also have the sides for the foot recess. The side pieces are $15 I show the stock parts from Brookville. They are #34. They want $110 for theirs