21st movement in HWA-RANG Tul, 35th movement in GE-BAEK Tul. 

This video shows the correct way to do 21st movement in HWA-RANG Tul (Niunja So Ap Goomuk Kaunde Baro Jirugi) and 35th movement in GE-BAEK Tul (Niunja So Joongji Joomuk Kaunde Jirugi)
Based on the explanatory scheme of foot movements from the taekwon-do encyclopedia, and the system of striking actions laid down in it, and from the point of view of the biomechanics of striking actions in taekwondo (ITF).