In step 30 of Empi, we begin facing west in left downblock posture. We turn northwest and do a slow rising palm block (teisho uke) with the right hand. In step 31, we turn to the north with a fleeting motion in which we press the right hand down and raise the left hand upward, both in teisho uke.
There is a move in aikijutsu (sode-tori nikajo-gatame) in which the opponent uses his left hand to grasp your right sleeve above the elbow. He is trying to control your right arm while he cocks his right arm for a punch.
Your response is to pull back a few inches, to straighten his arm, and place your right hand under his elbow, pressing upward. This is step 30 of Empi. Then you roll your hand over the top of his elbow, rolling his left arm in an ude gatame arm bar. His left wrist is caught in the fold of your right arm, so pressing down on his elbow forces him to his knees. It also makes him turn to your left, so your left "rising palm block" catches him under the chin (step 31 of the kata).
Here's a rough demonstration from http://www.aikijutsu.de/tori.html:
