From double pass thru formation: Leads do a Zoom 3/4 (to face each other) and Pass Thru (staying apart). Trailers step up and Half Square Thru. Finishes in lines facing out.
NOTE: Can also be thought of as Zip Code 2 and Half Square Thru.
Al Appleton 1976
This definition is from The Handbook of Modern Square Dancing by Jay King.
It is provided here for informational and educational purposes only.