When you need to make an effort to the nut and there are not enough hands, and the place is narrow and large adjustable spanners do not climb, you can use a tricky device. Of course, it is unlikely that it will be possible to unscrew large-sized rusted nuts with such a key, but he can easily cope with plastic plumbing.
For crafts, you need a thick steel plate or several small pieces, a long nut and a stud for 12 or 14. All parts are interconnected by electric welding, the key is turned and painted as desired.
The universal key was not large, you can always take it with you for plumbing.