A piece mark is the unique identifier given to each precast piece. It ties the physical piece in the yard back to its shop drawing, its place in the structure, and its spot on the load.
Marked on the piece and printed on its label, the piece mark is how the yard, the driver, and the erection crew all refer to the same thing. Good piece marking is what keeps the right piece going on the right truck to the right spot in the right order, which matters most when pieces have to be set in sequence.