1.sticky bit : regardless of directory’s access, only directory’s owner can delete files.
(only for directories)

$> chmod 01755 dirname
drwxr-xr-t

2.setuid bit: when you execute the program effective uid becomes as progams owner’s uid (such as passwd). Therefore , if execute bit is not set, this is meaningless

$> chmod 02755 exefile
rwxr-sr-x 
$> chmod 04755 exefile  
rwsr-xr-x