When I set permissions on a folder (CHMOD), besides the usual nine checkboxes for read/write/execute of me/group/all, there is an additional three checkboxes on the left, labelled st: g: and s:.

What do they stand for, and what do they change?

I can't find any documentation or help on this, can someone explain me?

(If that is relevant, I'm letting you know the version of FileMan I use is in French.)