Ah, also, I'm not sure if it makes a difference or not but I was in Architect mode.
********************EDIT******************
It won't let me add more replies (what a useless limitation...). Glad you got it!
Tip for gun show: put a weight bench in your canteen!
For some reason, on all of my games the prisoners would NEVER use the benches in the yard... I put one in the canteen and as soon as the next "eat" hour came around somebody jumped immediately on the bench and it popped!