Warp

These are the slide panels of 5 sun size. in many case, the slide panels of lid (The larger parts in the photo) may warp. The cause is humidity or dryness. If this parts warps, the Yosegi panels attached above it will also be affected. Therefore, the slide panels of lid larger than 5 sun size are made by combining three parts like this (arrow). This panels larger than 5 size is large and tends to warp. The direction in which wood warps is fixed (roughly speaking), so by arranged the wood grain as shown in this photo, the three parts prevent each other from warping. It is called "Hashibami"(in Japanese) in the Himitsu-bako production term. This is not done for Himitsu-bako smaller than 4 sun size because the slide panels are small (not easy to warp).