Combining with an engineering example, the author presents the methods of double queue piles, appliance conditions and questions that should be paid attention to in design and construction.

The queue used in each case is actually a deque (a double-ended queue, pronounced "deck"), which allows threads to steal work from the back end of another queue, balancing work entering the pool.

Fixed a case that caused the wrong dribble move to queue up when attempting to perform driving combo moves (e. g. double crossover).