Serra began to use lead in 1968 to enact sculptural processes such as rolling, tearing, and casting. However, he grew concerned that the finished works were mere records of the forces that formed them. He began to explore ways of making sculptures where forces continued to be at work at every moment of their existence. The two elements of Shovel Plate Prop push against one another in tension, the roll and sheet keeping one another in place. Propping is continuously active whenever the sculpture is installed.