A tool for facilitating accurate placement and installation of crown molding at an intersection of a ceiling and wall, the crown molding having a wall-engaging portion and a ceiling-engaging portion. The tool includes first and second extension arms, each extension arm having respective inner and outer major surfaces and respective proximal and distal ends. The first and second extension arms are connected together at their respective proximal ends such that their respective inner major surfaces face each other at right angles for receiving and orienting a sample section of the crown molding. The sample section includes a first longitudinal side edge representing the wall-engaging portion of the crown molding for residing adjacent the first extension arm and a opposing second longitudinal side edge representing the ceiling-engaging portion of the crown molding for residing adjacent the second extension arm. Measurement indicia are marked on each of the inner major surfaces of the first and second extension arms for measuring the sample section and determining the position of the crown molding at intersection of the ceiling and wall.