Abstract: A trailer cleanout portal assembly includes an inner bracket attached to an inner surface of a trailer perimeter wall. The inner bracket includes a first central aperture extending therethrough that is alignable with a wall aperture in the perimeter wall. A cover bracket is attached to the inner bracket with the perimeter wall positioned between the inner and cover brackets. The cover bracket has an access aperture extending therethrough that is aligned with the first central aperture. A panel positioned between the inner bracket and the cover bracket is vertically movable to open or close the access aperture. An open space is defined extending from a lower edge of the panel and between the cover bracket and the inner bracket such that material falling between the inner and cover brackets freely falls downwardly from the assembly.