A coupler system for connecting elongate, horizontally disposed rods to vertical supports includes a top-cap component for attaching to the top of a vertical support, and including a body with plural cavities formed therein, and at least one ball-cap component for attaching to an end of a rod, and including a ball region that is constructed to fit within one of the plural cavities of the top-cap component. The body may be formed with four of the plural cavities, with each of them having beveled edges. The ball-cap components may include a ball region, a neck region, and an angled region located adjacent the neck region and away from the ball region. The top-cap and ball-cap components may include insertion regions with opposing sets of ribs. The coupler system may further include a cover component, and the body may be formed with a central hole for receiving a fastener that secures the cover component to the top-cap component.