PURPOSE: To prevent damage in case the head of a crew in the rear set gets in touch with a sheet back of the front seat by sticking an elastic rubber plate on a reclining part of the sheet back enclosed with a sheet frame instead of disused wiring and spring below R5.

CONSTITUTION: A sheet frame 10 is formed of a pipe above R5, and a rubber plate 11 is stuck on said frame as a reclining part. The rubber plate 11 of shore hardness 60W90° is selected and a pad is appropriately taken out from the plate 11 except its upper end, both side ends, lower end and each fitting part 12W14. Then, the upper end fitting part 12 is fitted through sending round from the inside of the sheet frame 10 to its back, and a side end fitting part 13 is fitted on the front of said frame 10, while the lower end fitting part 14 is fitted through bending from the front to the back of the frame 10. Further care for the rubber plate 11 is taken such that metallic objects and the like with edge parts below R5 are not projected from the surface of the plate 11 except a part of its lower end surface where there is no possibility of contact between the head of a crew in the back seat and the sheet back.