Abstract: A sealing assembly particularly of the type used with a manhole cover or a height adjustment ring or structure for a manhole cover to facilitate a liquid type seal between the sealing surface of the cover and the mating surface of a support frame on which it rests. The assembly comprises specifically corresponding and cooperativetly dimensioned transverse dove tail configured groove and gasket arrangements both carried by the manhole cover wherein an outer peripheral portion of the gasket extends outwardly for sealing engagement with the mating surface on which the manhole cover rests when in its closed position.