Double nut trick for tight spaces - GIF

[BuffaloJohn]

Or - my solution that I have used many times is to put a piece of tape on the wrench down side, put the nut in the wrench and then screw the allthread into the nut and wrench away. I have used this on horizontal threads that were recessed pretty far as well, even crimped a thin wall tube to extend the wrench so I could reach further back...

A Handy Tool To Get A Nut In A Small Space