A main beam of a container semi-trailer provided with the joint, and the connecting method thereof. Each masonry unit can be placed on top of a previously placed masonry unit. A perforation located in proximity to the flap and adapted to facilitate opening of the envelope. An outer surface of the covering has a texture and finish that passes for the outer surface of the natural or manmade object the concealment represents. The rotational sensor may sense torque, such as with a piezoelectric sensor configured to detect rotational strain on a fixed pointing stick. One of the width and the thickness is reduced for receipt of a sensor about the busbar.