Clever, simple idea for a workholder that grabs automatically when you push a board into it, and releases automatically when you pull it out.  From medicinal chemist and woodworker Brian Grella.  From where I sit, it looks like you might only need to make one of these rotating cams, and the other side of the clamp could be a fixed, flat fence.  [via Instructables]

Bernoulli Spiral Clamps