This reminds me of an old Yiddish joke.  Yankel is out strolling and notices that Mendel the mohel has hung a large wooden sign over his storefront.  The sign is a wooden cutout of a man's hat.

Curious, Yankel enters the store and says, "Mendel, for what do you display over your storefront a hat?  You are a mohel, not a hatter!"

Replies Mendel: "Nu, then what should I display?"