How do you block directory scans using .htaccess?

From Joomla! Documentation

Directions

Add Apache rewrite rules to your .htaccess file. For example, the following will redirect all attempts to access files with names starting with, "phpMyAdmin" to index.php.

Sample Apache Rewrite Rule

RewriteRule ^/phpMyAdmin.*$ /index.php

Some Regular Expression Tips

^ Means start of filename
. Means any character other than newlines
* Means one or more of the previous character
$ Means end of line