4.0 likes s and S protections?

[Anthony A. Datri]

What's with all these s's and S's?

beaker% ls -ldg .
drwxrwsr-x 10 aad      developm      512 Dec 10 17:19 ./
beaker% pwd
/home/aad
beaker% chmod 700 .
beaker% ls -ldg .
drwx--S--- 10 aad      developm      512 Dec 10 17:19 ./
beaker% 
beaker% chmod 700 .
beaker% ls -ldg .
drwx--S--- 10 aad      developm      512 Dec 10 17:19 ./

[[ In this context, 's' means setgid and 'S' means setgid with no group
execute permission.  Now why permissions are set this way on directories I
don't know.  --wnl ]]