The H shape is the most powerful of the advanced letter shapes. When done in the correct order the H allows the player who made it to end the sequence of letters in a double open three, at least one of which will end in an open tessera. The H shape is made by choosing two of the four open tria threats available to the player in the X formation. If an open tria is made on opposite ends of the X shape so that a pattern resembling a capital H is formed, then the middle of the H creates an open tria at the same time one of the ends does. The opponent cannot block both so one of them can be formed into an open tessera.