US Patent 9289069 Seat for molded plastic chairs

A seat on a stool, chair or bench has permanent depressions in the surface of the seat that corresponds in shape to an end view of a human iliac bone. A pair of spaced apart permanent depressions are provided on an axis that passes through and is perpendicular to a centerline from the back edge of the seat. One depression is on one side of the centerline and the other depression is on an opposite side of the centerline. A third permanent depression is on the centerline and spaced apart from the axis that passes through the pair of spaced apart permanent depressions and is closer to the rear edge of the seat than the pair of spaced apart permanent depressions.