In the same stance, right forward back fist strike (oreun deung joomeok eolgool ape chigi) with left fist (wen deung joomeok) still supporting the blocking arm under the elbow.
Note: The upper-body should be twisted to generate more power for this back fist strike. It is a common mistake to dip the shoulders down while twisting the upper torso. Keep both shoulders level as the body is turned and twisted. The assisting fist should also remain as it is during this movement. This also applies to Movement 10.