Bed wood, square nuts, need your help

[hairdog]

I am a bit confounded, so I'd appreciate your help. The bed wood rails are held on by 3/8"bolts with square nuts. The nuts are, of course, inside the bed frame rails, underneath, which means a crescent or box end wrench will not reach. That leaves me with sockets.

A 9/16" socket (6 or 12 point) is too big to gain purchase on the square but. A 1/2" socket (6 or 12 point) is too small.

I can't find square nut sockets.

I need some guidance from my fellow truck owners, please.