A manhole assembly for a manhole having generally cylindrical sidewalls defined between an outside surface and an inside surface separated by a wall thickness and having a wall opening communicating the outside and inside sidewall surfaces of the manhole for insertion of a mating pipe. The wall opening defines a peripheral surface relatively perpendicular to the outside and inside sidewall surfaces which receives a ring shaped elastomeric gasket. The gasket has a retaining ring whose location is precisely determined to allow the gasket to be obliquely inserted within the wall opening of the manhole and to be subsequently snap-fitted into position on the peripheral surface, whereby the gasket is securely retained in a locked-in position with respect to the wall opening in the sidewall of the manhole.