Abstract: A lighting fixture and ceiling structure incorporating same are disclosed. The fixture may be securely mounted within a ceiling grid work assembly by a simple downward movement of the fixture. Ceiling board is supported by being mounted on flanges integral with the fixture on the one hand and elements of the supporting grid on the other. The fixture and grid work interact so as to effect an accurate positioning of the fixture relative to the grid work by taking advantage of centering formations integral with the grid work.

Abstract: The present invention is directed to a moisture sealed and vandal-resistant lighting fixture and is characterized by novel means for securing a diffuser in tightly sealed engagement against a gasket on the housing of a lighting fixture, which means precludes the ingress of moisture and reduces the likelihood that the fixture may be vandalized. More particularly, the invention relates to a lighting fixture, preferably rectangular, wherein the diffuser component is pressed against the mouth portion of the housing component by a cam arrangement, access to the cam arrangement being provided through a wall of the housing via an inconspicuous aperture or apertures whereby only one who is familiar with the operating characteristics of the fixture would recognize how to release the cam arrangement and, hence, the diffuser.