An assay device is provided which includes a support, generally planar and elongated in shape, upon which a biological binding reaction may take place. This assay support includes in its broadest aspect, three sections, a sample receiving well section at one end and a gripping section at the opposite end, with a connecting section therebetween. The sample receiving well section includes at least two spaced-apart receiving wells, generally at the end of the assay support, for the addition of binding reactants. Each of the wells has an open end on a first face of the support, a concave inner surface extending concavely into the support, and a convex outer surface which projects convexly from an opposed face of the support. These wells may serve as a depository to contain aliquots of binding reagents, as well as a sample under analysis, the sample under analysis possibly containing a substance that will bind to the binding reagents.