Abstract: A fluid filter and a method of constructing a fluid filter which will independently retain itself in a fluid passageway includes a sheet of filter media and a retainer which is attachable to one side of the filter media. The retainer may be sized to frictionally engage the walls of the fluid passageway or may be of a resilient material which allows the retainer to resiliently engage the walls of the passageway. The retainer is attached around only the periphery of the filter media with the central portion of the filter media being free with the respect to the retainer. The filter media has flexible edges which extend beyond the retainer to seal the passageway so that all fluid flowing through the passageway will flow through the filter media.