The detection of flaws in constructional materials by manual ultrasonic scanning has proved its efficiency over more than thirty years. An almost irreplaceable advantage of the manual scanning operation is the flexibility in movement of the ultrasonic search unit. However, disadvantages are the restricted reproducibility and reliability of the results obtained. A further restriction is the human inability to comprehend and correlate the full content of information which the screen images of the ultrasonic testing instrument display. Finally, the relatively low speed at which a manual inspection can be carried out is an important restriction too. Mechanical ultrasonic testing has overcome several of these difficulties and enables direct readable results to be obtained and storage of data if periodic inspections are envisaged. A number of ultrasonic search units can be used simultaneously and previously programmed with regard to their function, the volume to be tested and sensitivity. The data collected may be evaluated automatically according to built-in criteria.