Specifies materials, dimensions and manufacture of seven different types of calibration blocks, and of calibration and reference blocks containing flat-bottomed holes. Procedures for use of each block in the calibration of equipment/probe combinations are described. Step by step procedures are included for assessment of vertical and horizontal linearity, and overall system gain, and for measurement of dominant frequency, pulse length, beam angle, alignment of beam and procedures for calibrating test equipment used for thickness measurements. Guidance on the frequency of calibration of test equipment is given in an appendix.