The three difference between positive and negative plates. The selection, three ply to grain clear and smooth smooth front handle. No delay should not be damaged, damaged, flawed, section scar defect, cutting surface without debonding. Some three ply is two single in different lines of the stick together made, so in the choice to pay attention to splint seams should be tight. The selection of three plates, three plates of various parts of knock by hand, the sound crisp, shows good quality. If the sound muffled, said the plywood has been scattered glue phenomenon.