Erie Scientific (now part of Thermo Scientific) of Portsmouth, NH, has received US Patent No. 7,943,093, "Cover slip." The cover slip described can be used as part of a chamber for a hybridization reaction. The slip has a surface and two substantially parallel, opposed edges binding that surface. A spacer has a pair of spacer segments, and each spacer segment extends along substantially a full length of a different one of the opposed edges, forming a chamber between the spacer segments, the cover slip, and the substrate.