A coupler having a support provided through the body of the coupler and a plurality of openings in the coupler which are configured as open cavities. The coupler structure includes a shank that has a vertical support as well as lateral support. The coupler may be configured with a double I-beam structure with openings into the shank. Cores that may be fixed to the mold may be used to form the coupler and produce the openings in the shank.