During ultrasonic testing by the immersion method, it is frequently necessary to angulate the search unit when a discontinuity is located at an angle in order to:

Avoid a large number of back reflections that could interfere with a normal test pattern

Obtain a maximum response if the discontinuity is not originally oriented perpendicular to the ultrasonic beam

Obtain a discontinuity indication of the same height as the indication from the flat bottomed hole in a reference block

Obtain the maximum number of entry surface reflections