Abstract: Connector apparatus for joining structural components, such as posts 19 and panels 25, to form a modular structure. Posts are extruded members with T-shaped grooves 21 therein. Affixed to the panels are grooved rails 27 with corresponding T-shaped grooves. An adjacently positioned grooved post and panel rails are joined by connector assembly 31 which consists of two C-shaped channels 33 and 35, and a plurality of transversely extending threaded elements 39 that are threadedly engaged to the channels. The threaded elements have left and right hand threaded ends 38 and 40, each end threadedly engaging one channel, and when rotated, act to increase or decrease the distance between channels to lock or unlock the panel to the post. Periodically spaced slots 47 in the channel webs or on a U-shaped member secured to the webs permit brackets 48 to be mounted to the connector apparatus.