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.
From a right-handed box, everybody does the first part. This brings the original trailers into the center, holding left hands with each other. Only these two dancers do the second part. The other dancers are done and simply wait for the center dancers to finish the second turn.
Note that this is very similar to Swing Thru, except that the first turn is 1/4 instead of 1/2. Like Swing Thru, the first turn is always by the right.
This means that for a 1/4 Thru from left-handed waves, since only the center dancers are holding right hands, only the centers do the first part. Then just the two who come into the very center can turn by the left for the second part.
Of course there is also Left 1/4 Thru. This means that first those who can turn left 1/4, and then those who can turn right 1/2.
3/4 Thru is the same as 1/4 Thru except that the first turn is 3/4. The second turn is still 1/2.