8–8–16, n. — Green’s Dictionary of Slang

8–8–16 n.

[the dimensions in inches of a single one of the concrete blocks that make up the walls of a prison cell]

(US Und.) a prison cell.

1992

Bentley & Corbett Prison Sl. 6: 8-8-16 A concrete block prison cell. This stands for 8” x 8” x 16”. These are the dimensions of a concrete construction block.