Htaccess help - 404 redirect

[aceofspades]

Hi,

1. I was wondering, can anyone tell me two things about htaccess. Firstly, is it possible to comment in an htaccess, if so, which method must be used?
   
2. Redirect any addresses within that folder to a 404 error. I also dont want to hardcode the htaccess with the link if I can help it, so I can put this file in lots of folders to do the same job without having to change the code each time.

folder/index.html ----> 404
folder/test/test.jpg ----> 404
folder/test ----> 404

This is the code im starting with, it doesnt work however, as it was only a guess:

RewriteRule ^(.*)$ ../$1 [R=404,L]