Check Washing

We've discussed this in some of my classes.

Thieves can remove ink from your check and re-write it without compromising any safeguards, including your legitimate signature. Takes forgery to a new level.

Here is a great illustration if YouTube lets the video stay up.
http://www.youtube.com/watch?v=iwUTvIyRvdk

Watch this if you write checks, or accept them for that matter.