A system of discards in which the face value (odd/even) of the discard may signal attitude or suit preference. Even cards Encourage the suit discarded while odd cards are off-putting (discouraging) and asks for the other suit of the same colour.
For instance, when discarding on a spade lead, the ♥2 asks for a heart, the ♥3 asks for a diamond and the ♣5 is neutral (as it theoretically asks for a spade).