Operation On-Target Quad Mirror Assembled, Rear (6 of 8)
This is an example of the classic tripod-mounted quadruple mirror, made of four 12"x12" mirrors mounted onto a board, used for the BSA Varsity Scout mountaintop to mountain top mirror-flashing activity, Operation On-Target. See en.wikipedia.org/wiki/Operation_On-Target for more information.
This closeup of the board before mounting to the tripod shows the rubber washers, fender washers, and turnscrews in more detail. (#6 in a series of 8 photos)