Okay. I think I get it now. Is the bottom of the center portion of the "C" recessed compared to the outstanding legs? I am assuming it is, and that the legs straddle the film/paper base, right?

Assuming the above is correct, why use two screws at each end instead of spreading them out along the blade to give better support? I'm guessing that my conservative nature is coming out and that the blade is stiff enough and the emulsion viscous enough that you don't anticipate much deflection in the blade?