A method and apparatus for holding a part on a fixture in a precisely known predetermined position includes pressing a surface of the part against a vacuum head and sealing an annular elastomeric sealing ring against the part surface. A valve button of a valve is engaged by the part surface to open the valve and establish communication between a vacuum source. The part is pulled by the vacuum against a hard stop in the vacuum head having a fixed precisely known relationship to said vacuum head reference surface. The hard-stop can be mounted in the base of the vacuum head for pivoting about at least one axis to self-align the hard-stop face with the part face.