Abstract: A jig device for accurately measuring an opening when installing shelving, windowsills, molding, and similar construction material is provided. The jig device comprises a first elongated bar and a second elongated bar. First incremental measurements are marked on the first elongated bar with the first incremental markings reading right to left. Second incremental measurements are marked on the second elongated bar with the second incremental markings reading left to right. A first fastening mechanism slidably connects the first elongated bar to the second elongated bar and is tightenable to inhibit movement between the first elongated bar and the second elongated bar. A first angle paddle and a second angle paddle are provided.