How do I start digging a tunnel under my toilet?

Prison Architect has just released their new escape mode. Its pretty cool, but I dont know how to start digging a tunnel. I find the wooden pick-axe, bring it back to my cell and left click. However, this only damages the toilet which eventually calls the guards. How do I dig under it instead of damaging it?


I figured it out:

Once you have a tool equipped you can walk over to the toilet and right click on the toilet.