salt

As the story goes, in the old days, crusty old wayfarers upon sitting down to meat, would stick their knife into the salt jar or bag. As they withdrew their knife they made sure there was an amount of salt resting on the blade. They'd hold the knife over their food and tap it with their fingers, knocking the salt off somewhat evenly onto their food.

[What? You think I'd make something like that up?]

SALT:
The left hand stays stationary. The right index and middle fingers alternate moving up and down.

Sign: salt