Box Select Tool does not disappear Not sure if this is a bug or feature.

I was using the box select tool to join a couple of objects together. Suddenly a box froze and did not select anything, I could keep using that tool but that box would not disappear.



How can I get rid of thar box? Reloading the file, or even closing blender and running it again does not make it go away! Thanks for the time.
The red box is your render border (what you want to render) This helps reduce render time if you just want to see what part of your scene will look like. Instead of rendering the entire scene everytime. 

To get rid of it: press Ctrl+Alt+B.

More info can be found here: Render just part of a final image from Cycles?