My cats are indoor 99% of the time. If I am sitting on my patio, I will let the herd 'graze'..but, I am in constant contact with them, and the door is completely opened. I have a fenced in back yard, and as strange as it sounds...my cats don't go anywhere! I won't let Minnie out- ever, and the newest one- nope, can't do it. I am too afraid she will run away.