Eftersom huvuddelen av filmens historia handlar om att sakna heroin ...
The title refers to a block of heroin, compressed roughly to the size and shape of a brick.
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At The Pin's house, Tug tells Brendan that The Pin received a shipment of ten bricks and sold eight; one was stolen and replaced with another that had been doctored with detergent, causing Frisco's coma, and the 10th brick remains to be sold.