This "quick tutorial" introduces the general idea of a call and explains the most common cases. It does not explain or illustrate all cases. For additional details and/or examples, refer to the links in the "MORE INFO" box.
Dancers who are lined up in a column of four, all directly facing the center of the column, do a Double Pass Thru by walking forward past both dancers who are facing toward them. They each move slightly to the left, so that the dancers they are passing will be to their right. Once they have passed both dancers coming the other way, they move over again, slightly to the right, so that they are all lined up in a straight column again, all facing away from the center of the column.
Usually two parallel columns are doing this at the same time. The dancers standing next to each other will drop hands at the beginning, and then take hands again at the end, after they have passed the dancers coming in the opposite direction