Abstract: A joinder piece for connection of sectional or segmental support members, at least one of the support members having a plurality of aligned slots to receive seating hooks of a cantilever bracket, comprises an elongate body having an opening or trough which is partially inserted into at least one of the support members. The elongate body has a base portion bordered by a first side portion and a second side portion to form the opening or trough opposite the base portion which is capable of being disposed in alignment with the plurality of aligned slots of the support member. The base portion of the elongate body preferably has an indentation to divide the base portion into a first base portion section and a second base portion section which are non-linear along their combined external base portion surfaces. The base portion may also have an inwardly extending ridge along at least a part of its length.