Yes, the brass fits under the latch, but I've found that the rings which surround the pinholes hold the plate tightly enough to the camera that the latch isn't needed. The rings were created by taking 1/32" basswood strips, soaking them in water and using the lens mount on the body and/or a metal pipe as a form in/on which to dry them. Two such rings were then glued together to create a seamless 1/16" thick wood ring that fits the camera perfectly. There may (must?) be an easier way to do this... Also, I've found that it is easier to make a bunch of these plates all at once, given the excessive labor my approach involves.
The rise works like rise in a large format camera, to help limit converging verticals. The large format people could probably explain the benefits in more detail.
The pinholes came from the manufacturer (see http://www.pinholeresource.com) with a chart of the optimum focal length for each one and the exposure require. This info appears on a legend on the back of the lens.
Generally I just point the camera at the target, see if anything appears on the viewing screen and shoot. I don't use these as much as I should, so REAL pinhole photographers can probably provide more information on technique.
Originally Posted by mdohoney