I thought this was kind of amusing. I managed to mount an M42-thread adapter onto a lens board for my speed graphic:
But it's not quite as insane as it looks. I'm not going to be shooting the Helios-44 with it (maybe for extreme macro? probably wouldn't be very sharp though).
This gives me an easy way to mount small lenses. Easy in the sense that I just have to drill one of the dozens of M42 body caps I have and affix the lens to it.