The height (Z coordinate) up to which a block that is being moved by HandleRisingBlock or HandleMovingBlock rises after it has been pushed down. It is set from the block that is handled first while it is zero (HandleRisingBlock adds 48 to the height of its block) and it is cleared when a room is built. The use of the height is inferred from HandleMovingBlock_TestHighestPoint, where the rising stops once a block is higher than it.