Two dancers who are directly facing each other Pass Thru by walking forward, without turning. To get past each other, they each move slightly to the left, so that their right shoulders pass by. But once they have passed, they move over again, slightly to the right, to be directly back-to-back.
Often multiple dancers standing side by side will be doing a Pass Thru at the same time. In this kind of situation, they must first drop hands. When they get to the other side they are each directly back-to-back with the person they had been facing, and they take hands again.