Facing Tandems
Dancers move forward until all dancers have passed two other dancers. Dancers pass right shoulders.
Back-to-Back Tandems
4
Same as for Pass Thru
Double Pass Thru is a four-dancer call, but it is most commonly used from the eight-dancer formation of a Double Pass Thru (which is two side-by-side Facing Tandems).
The Ocean Wave Rule applies to this call. That is, it can begin from a Right-Hand 1/4 Tag (or a Right-Hand Single 1/4 Tag).
Except for applications of the Ocean Wave Rule, dancers must start facing each other, rather than offset. For example, Heads Star Thru, Boys Double Pass Thru is improper. However, "Heads Star Thru, Boys On A Diagonal, Double Pass Thru" is a proper extension and ends in Left-Hand Columns.
The "Double" in Double Pass Thru refers to the number of dancers passed by each dancer. When extended, the call would be Triple Pass Thru (from facing Tandems of 3) or Quadruple Pass Thru (from facing Tandems of 4). Dancers are not expected to know these variations without an explanation.
From normal Facing Couples, the sequence Right and Left Thru, Put the Ladies in the Lead (or simply Ladies Lead), All Double Pass Thru relies on directional calling. See the section "Additional Detail: Directional Calling".