I purchased one of those gag signs with CFMan in mind. It said:
Please observe the following rules:
1. If you open it, shut it.
2. If you turn it on, turn it off.
3. If it's trash, throw it out.
4. If you take it out, put it back.
5. If you make a mess, clean it up.
...that's the gist of it.
CFman took one look at it and said, "That's a great sign. I need one of those to put up at the CF trailer. It says it all in a nutshell." (This from the man who leaves used paper towels lying on the counter, the air conditioner running, the refrigerator door open, and on...)
I just laughed and said, "Happy Father's Day!"