An apparatus for training athletes having two supporting structures. The first structure has a base that can rest on a surface and walls that extend upward from the base to an upper end, defining an interior space. The walls incorporate a bar connector above the base designed to connect to and support one end of a bar. The walls have supporting elements above the base and below the upper end of the walls. The second structure has walls that are configured so that the lower end of the walls can engage the supporting elements of the first structure so that the second structure is supported by the first structure above the supporting elements. The second structure has a bar connector at the same height as the height of the bar connector of the first structure configured to connect to and support the other end of the bar.