The present invention discloses a rectangular ceiling module, accessible one by one, that allows the use of larger-than-standard, reduced-thickness formats, with a front face, a rear face and four edges, with corners forming obtuse angles and robust geometry; it is installed from below without surpassing the height of the standard support grid; it rests on the grid by its four edges or sides and leaves the grid hidden. The module is useful as a standard false ceiling, hiding air-conditioning installations, electrical installations, fire-protection systems, low-current systems, etc., located under the slab, mostly in office buildings, while also serving as an element of insulation and/or sound absorption, depending on the material used.