Convertible trailer

A container for a convertible trailer including a chassis for carrying the container and a set of wheels for rollably supporting the chassis on the ground, the container comprising

• a floor,
• a wall,
• a roof, and
• an access door for loading loosely compressed materials into the container, the roof including a pair of opposite rigid panels, respectively pivotally connected to opposite side walls of the container by multiple hinges for movement between a closed position wherein each panel forms part of a solid roof for loading of the container with loosely compressed materials from the access door, and an open position wherein the container can be loaded from the top with bulk material, and a plurality of spaced apart locking bars distributed in longitudinal direction of the roof, for selectively maintaining the panels in the closed position against outward pressure exerted by the loosely compressed materials when loaded in the container and for strengthening the wall against the outward pressure, a spacing of the locking bars being smaller proximal to than distal from the access door.