I was playing my BB1100S fretless earlier and thought I'd lower the action a smidge. Had a look down the neck and decided it could do with taking some relief out rather than lowering the saddles.
I remembered the previous owner saying there was an adaptor on the trussrod that he'd left on to make adjustments easier, but had thought no more about it.
When I had a proper look to adjust it, it turns someone has taken an 8mm 1/4 drive socket and drilled four holes through it to allow you to put a small screwdriver or allen key through and turn it if you don't have the proper 8mm trussrod wrench.
What a genius idea. It stays snuggly in place held by the wood of the neck but turns easily.
With a flatter board and some overdrive it absolutely growls now, mwaaaaaaaaaaaaaaaaaaaah for days.
Socket left in place,
The trussrod nut,
The 8mm socket,