| 摘要 |
PURPOSE:To prevent the occurrence of unsteadiness by forming a divided section in the direction of a diagonal line of a top sheet and opposing divided end edges of the divided section to each other in a state of contact. CONSTITUTION:A top sheet 1 is divided into about triangles by a diagonal line or in the vicinity thereof to form a divided section 5, and divided end edges 8 of the divided section 5 are opposed to each other to form a square. A bottom sheet is provided to the rear of the top sheet 1 to form a free access flooring. |
