The Subtraction Working Charts (C 106-2) provide children in the lower elementary years with a self-correcting reference tool for building fluency in subtraction facts after initial concrete work with the stamp game and bead frame. These large-format charts allow children to verify their own work independently, supporting the transition from manipulative-based computation toward abstraction. Having a classroom set ensures multiple children can work through subtraction operations simultaneously without bottlenecking at a single chart.