Avoiding conflict

You can always tell if a store owner has gotten fed up with a particular issue or complaint when he or she puts up a sign to deal with it.  Think about the signs at grocery stores and other places that sell cigarettes and beer: "We ID Under XX" implies that if you are under XX, you need to have your ID ready or put the beer and smokes back.   "We do not sell firewood," really says, "Please stop asking for firewood."  "Donated items only" indicates that the food bank people are tired of sorting the garbage out of the food collection bin.

Of course, sometimes a sign made for such a reason gives an unintended message.

Such as, "I'm a jerk." 

And apparently a jerk without much background in the difference between to and too.

Just don't ask us to proofread them.

I have to admit, though: it's a good-looking sign.  You know, except for the glaring misuse of an apostrophe.