I have used 3 x 7 cm and larger thru hole prototype boards to build small circuits for some time. Recently I used them to assemble circuitry to drive a servo turnout motor (see servo mount under model trains on Thingiverse) on a friends model railroad layout and I needed to be able to screw (#4 or M3) the board to the underside of the layout. I designed the enclosed mount to do that, but it clearly could be used to mount the board in most any project.