In the manufacturing of typical quartz crystal resonators, wafers are cut from a quartz crystal bar into plates, called crystal blanks, along precisely controlled directions with respect to the crystallographic axes. The cutting is usually done with a slurry saw which consists of a set of approximately 100 thin, stretched metal bands moving back and forth across multiple quartz bars in a flood of abrasive slurry. The properties of the resonator depend strongly on the angles of cut which are determined by x-ray diffraction. After shaping to the required dimensions, lapping, etching, polishing and cleaning, metal electrodes are applied to the plates which are mounted into holder structures. The plates are bonded to the mounting clips of the holder with a silver-filled epoxy or polyimide. The assembly, called a crystal resonator is hermetically sealed. The flow chart here shows the major steps in the fabrication of a resonator. Although all the steps can affect the stability, the steps shown in the box are usually the most important with respect to the long term stability of the resonator. The final steps are performed in an ultra-high vacuum. Ultra-high vacuum baking immediately before hermetic sealing is highly desirable in order to produce low aging, especially if the resonator is exposed to air after frequency adjustment.