Figure 1.

The first step of framework training using a plastic eraser. Schoolchildren engrave a postcard-sized plastic eraser in art class (a). The conjoint sixth and seventh ribs and a long piece of the eighth rib cartilage are drawn on one of the plastic erasers that was cut out into four pieces (b). The rib cartilage models are carved out and split into two pieces each with a thickness of 5 mm (c)