Unfinished Red Oak Hardwood 0.17 in. Thick x 0.3 in. Wide x 4 ft Length Spline, $1.96 USD/Box, LL Flooring (Lumber Liquidators)

This spline, or Slip Tongue, fits into the groove of hardwood flooring so the direction of nailing can be reversed. Measuring 0.17 in. thick x 0.3 in. wide x 4 ft length, it is suitable for various hardwood flooring applications.