joey@veritas:/tmp$ mkdir a
joey@veritas:/tmp$ touch a/b
joey@veritas:/tmp$ chmod 0400 a
joey@veritas:/tmp$ ls -al a
ls: cannot access 'a/.': Permission denied
ls: cannot access 'a/..': Permission denied
ls: cannot access 'a/b': Permission denied
total 0
d????????? ? ? ? ?            ? .
d????????? ? ? ? ?            ? ..
-????????? ? ? ? ?            ? b
joey@veritas:/tmp$ chmod 0500 a
joey@veritas:/tmp$ ls -al a
total 0
dr-x------ 2 joey joey 15 Jun 16 20:47 .
drwxrwxr-x 3 joey joey 15 Jun 16 20:47 ..
-rw-rw-r-- 1 joey joey  0 Jun 16 20:47 b