Ever wonder how exactly a sentry gun works, and what the many options actually do? Well, this is for all you die-hard TF2 fans. I found this great PDF with lots of great material on the Engineer and his Sentry Gun! Click the image to view the manual.

This was found at the following link: http://www.steampowered.com/v/index.php?area=game&AppId=440&cc=US