Abstract: An upright panel having an upwardly-opening top channel extending along the upper edge, which channel is closed off by a top cap. Spring retainers releasably engage the underside of the top cap, and in turn releasably secure the top cap to the panel. Each spring retainer has sidewardly-spaced upwardly cantilevered spring legs which have hooks for engagement within retaining channels provided on the underside of the top cap. An arched spring part extends sidewardly between the spring legs adjacent the lower ends thereof. This arched part is normally positioned downwardly from the underside of the top cap. Sidewardly-spaced downwardly cantilevered spring legs extend downwardly from the upper spring legs, and at their lower ends have sidewardly projecting cams which project under the channel top flanges. During removal of the top cap, the upper and lower spring legs initially jointly deflect inwardly about the top hooks, and this causes resilient deflection of the arched part until it abuts the top cap.