a vent check valve having a relatively flat configuration of its elements , being thereby adapted to utilize a local wall area of a housing to be vented as a supporting body and to provide a valve seat . the valve elements include an elastomeric flat diaphragm and a retainer for holding the diaphragm against the valve seat . these elements are disposed in respective counterbores formed in the wall body concentrically with the valve seat . the retainer has a spiderlike configuration with circumferential legs dimensioned to flex rearwardly in the associated counterbore upon installation to produce a self - locking wedge fit therein .