Foam stop is applied to the ledge side below the film rails.
This stop provides support for the sides of the filter and also
acts as a light seal. The strip is placed so that it is on the same plane
as the grooves for the film rollers.

To apply the stops, open the focal plane shutter on "B" with a locking cable release
and lock the mirror up. Stick one end flush with top or bottom edge and maintain
the same distance from the film rails and press the adhesive to the side as you go.

There should be about 1mm clearance to the shutter curtains.
Clearance below the film rails (film) is also about 1mm.