Here the two wooden plates have been fastened together with the
pinhole plate sandwiched between them. The flap shutter is fabricated
from some 0.020 inch (0.5 mm) matte black anodized aluminum scrap,
cut to shape and a small flange folded up to stiffen it. The two
round head brass screws above and below the lever limit the travel.
There is a paper washer underneath the lever at the pivot screw.
Careful adjustment of the screw provides enough friction to hold
the shutter wherever it is positioned, handy for long exposures.