You Can't See Me

Truckers have important information printed on the backs of their trailers. It is a public service reminder about driving: "If you can't see my mirrors, I can't see you".
We should post a similar sign in the pharmacy. If you can't see me, I can't see you.

How many people have stood just far enough behind the counter as to be hidden by the post? Or the gate? Or the privacy divider?
They are the first to become agitated when you've managed to not see them for a what feels like an eternity, often 7-11 seconds.
While I do not encourage the fake cough, the throat clear, the key jangle, the counter slam, the key drop, the giant sniff, or the loud "HELLO!?", simply stepping forward or to the side may produce the desired result of being seen.

http://youtu.be/zekiZYSVdeQ