The invention relates to a system of self-adjusting straps that allow the weight or load contained in the element-holding object, such as a briefcase, backpack or suitcase, to be distributed evenly and automatically over the user's two shoulders, ensuring that the object is perfectly balanced and that it fits ergonomically on the user's back. The invention also to a rear protection mechanism with a magnetic opening system, intended for objects used to hold elements, such as, for example, briefcases, backpacks or suitcases. The mechanism acts an anti-theft system for rear, side and/or lower pockets on said objects. The rear mechanism with a magnetic opening system comprises flaps with non-visible magnets located inside said flaps, which, upon coming into contact with other magnets located on the rear surface of the object, generates an attraction that secures the flaps.