Bind in fstab

hi, i'm trying to add an entry in my fstab for the equivalent of mount --bind /a/b/c /x/y/z where /a/b/c and /x/y/z are just directories. i've tried: /a/b/c /x/y/z bind bind 0 0 and some other variations (including /dev/hdb3/a/b/c, etc). but everytime, it says /a/b/c can't be found. can someone tell me the proper entry in fstab for these binds? thank you xiaolei