From HomoExcelsior

1. A pattern or gauge, such as a thin metal plate with a cut pattern, used as a guide in making something accurately, as in woodworking. 2. A horizontal piece of stone or timber used to distribute weight or pressure, as over a door frame. 3. A molecule of a nucleic acid, such as DNA, that serves as a pattern or mold for the synthesis of a macromolecule, as of RNA.

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