[dkpbxman]

When I had to swap out the stems (made by Sayco) in my shower I got a set of shower valve sockets especially made for that purpose but when I fit it before applying force, I found that it didn't fit exactly.
I was afraid that if I did try to force it, the socket would slip and just round over the soft brass(?). I didn't know what I'd do then.

What I did was to use an old, everyday socket that I had in the closet that fit "a lot more tightly".
The socket fit over the bonnet nut of the stem if you pushed it into the wall and the long stem fit through the drive hole of the socket.
There was still enough of the socket protruding that I could grab onto it with my channel locks and slowly turn.