Bato - named after Bato Protega

Lead Q from suit bid. Dummy holds 3 cards in this suit. Partner plays high spot card. Next leader plays A (or K), showing AKQ. partner playz low showing a doubleton. Next leader plays high or low spot, thus forcing partner to ruff.

Convention: 

High spot by leader requires ruff as high as possible, to promote leader's trump (she knows that declarer, too, holds a doubleton).

Low spot by leader requires to ruff and shift to the suit indicated by A or K (she knows that declarer, holds 3 cards in the suit)