Abstract: In one embodiment, a system, comprising: a control system; a pivot arm assembly, the pivot arm assembly comprising plural arms joined by a transverse arm; and plural electromagnetic assemblies, each comprising an electromagnetic device, wherein the control system is configured to selectively activate each electromagnetic device when the plural arms are in contact with the plural electromagnetic assemblies to magnetically constrain movement of the plural arms relative to the plural electromagnetic assemblies.

Abstract: A tarpaulin support device for an open top of a trailer or vehicle. The device has a flexible and resilient tube assembly bowed from a normally straight position under tension to an arched position outwardly from the trailer or vehicle. The tube assembly may be removably mounted to the side walls of the trailer or vehicle via brackets with angled bores therethrough. The tube assembly comprises an outer tube and an inner tube located substantially within an outer tube. The inner tube may have a slot running along at least part of its length, such that the portion of the inner tube with the slot has a C-shaped cross-section.