Cool - Are they epoxied together, or just butted dry?
I think they were just butted up dry against each other but I didn't try to pick them up so I'm not totally sure.
I thought it could have been that the one up against the wall was there to prevent the one he's using for sharpening from slipping up on a slippery tile.
He was using the full length of both stones on his passes.
That looks very ergonomic.