Warning

The warning signal enables the giver to warn the taker about upcoming problems in a suit. If the taker leads the $\spadesuit$K and the giver has $\spadesuit$A, $\spadesuit$4, and $\spadesuit$3 she will play the three first and follow it with the four on the next spade. This unusual play, a lower card followed by a higher card in the same suit, tells taker that bad things are about to happen in the suit. The taker should immediately look elsewhere for pitches.

This signal has no risk if the two cards that giver is going to signal with are touching.

If they are not then there is a bit of risk in showing the signal. The farther apart the two signal cards are, the more risky it is.

Never show this signal if you have three cards below taker's initial lead in the suit.