The boy lifts his right arm while the girl lifts her left arm, and they keep their hands together loosely to form an arch. They turn to face each other (the boy turning right and the girl turning left) and walk forward, and as they start to pass each other the girl "goes under the arch" and continues to turn to her left. Meanwhile the boy walks around the girl, continuing to turn to his right, and ending up standing to her left. When they are done they lower their hands to the usual height.
The walking and turning are all done as one continuous action, with the girl walking in a small semi-circle to her left, and the boy walking in a slightly larger semi-circle to his right. Each dancer turns exactly 1/2 (180 degrees), to face the opposite wall.