A runner for an extension table that has two sliding leaves includes a wooden primary transverse beam with a side, a wooden secondary transverse beam attached securely to the side of the primary transverse beam and a track assembly attached to the side of the primary transverse beam. The secondary transverse beam has a top. The track assembly is supported by being fitted on the top of the secondary transverse beam. Therefore, the secondary transverse beam provides a robust support to the track assembly to prevent that from being deformed or separated when the track assembly undergoes an accumulated weight caused by stacking the extension tables during a period of transport or storage.