A sand beach chair formed of panels mounted to a frame includes a seat, a seatback extension pivotably mounted to the seat, and a seatback extension pivotably mounted to the seatback extension. Beads that have a U-shaped concave portion when viewed in a cross-section of the vehicle are provided at a rear portion of the floor panel, and the beads are aligned with the concave portion of the stiffeners and are provided continuously with the stiffeners. The handle portion 9 is slidably and fixably provided at the base portion 72 of the frame portion 7. Visualization by irradiation of the photochrome or near IR dye can improve detection of the polymeric matrix on a device or in the body.