Hardwood floor system including a piece of sponge, e-shaped plastic racks with ribs whose projections engage the shoulders and inclined surfaces of a plurality of floor boards

Structure of a hardwood floor comprising:

• a piece of sponge;
• a plurality of floor boards each being a generally square or rectangular member composed of an upper portion, an intermediate portion and a lower portion, said upper portion having a top surface for walking, said intermediate portion having a protruded flange extending outwardly from two adjacent lateral sides thereof and a recess on another two adjacent lateral sides thereof, said protruded flange being configured and sized to engage with said recess, said lower portion having an inclined upper edge along a longitudinal side thereof, an inclined lower edge along another longitudinal side thereof, and a shoulder above said inclined lower edge;
• a plurality of plastic racks with an E-shaped cross section having a plurality of ribs extending upwardly from a top thereof, each of said ribs having an enlarged head with an inclined surface thereby forming a lower projection at one side adapted to be positioned on said shoulder of a respective one of said floor board and an upper projection at another side adapted to be positioned on said inclined upper edge of a respective one of said floor boards, a top of a respective one of said racks having a center line for providing position reference and a plurality of through holes.