a first elastic module mounting part including a first base layer having a first base layer upper surface and a first base layer lower surface, wherein an outer edge of the first base layer upper surface has first stop edges extending to a predetermined height;

a plurality of first elastic modules disposed on the first base layer upper surface between the first stop edges in a predetermined pattern; and

a pad layer laid on the plurality of first elastic modules;

wherein an outer edge of the pad layer and the first stop edges are connected via a releasable first connection structure, the elastic pad having no side surrounding cover;

wherein the first base layer upper surface has a plurality of first positioning rails arranged at intervals in a lengthwise direction of the elastic pad, each of the first positioning rails extending along a width direction of the elastic pad, and first elastic module mounting areas respectively formed between adjacent first positioning rails, wherein in the width direction of the elastic pad, each of the first elastic modules is configured to form a sliding fit with an adjacent first positioning rail at either end of the adjacent first positioning rail to slide into the first elastic module mounting area, and further slide along the first positioning rail to a set position, so that each of the first elastic module mounting areas is provided with a plurality of the first elastic modules;

wherein the plurality of the first positioning rails are located between the first stop edges, and the first stop edges are configured to stop movement of the first elastic modules in the width direction of the elastic pad.