When I leave my pup at home in her crate I alway leave Gillian Welch's "Harrow and The Harvest" playing, and leave KQED on the television. This is so she can't hear the dogs at the dog park outside our window.
I like to think she's a pretty sophisticated canine!!!
However, this means my housemates don't always know she's alone and don't know to let her out. Sooooo, I made this door tag. I made it at Techshop!
I'm also making one for my acupuncture clinic: it will say "session in progress." That's what the illustrator template says, which is attached to this instructable. Caveat:
I'm going to show you the photos of my first attempt. I realized I mis-guessed the measurement to fit on an actual doorknob. So as you can see I hung it on a nail. To avoid this use my illustrator template, which is 4.25" width by 11" height. If your cut is 4.25" wide and you make a sizable round hole at the top then it'll fit over the door knob.
I made it this size in case you want to use an 8.5x11" piece of fancy paper instead of wood. I'm going to see if I can link to my new illustrator CS3 template.