When one sits face to face with another on the toilet…legs spread on the bottombunk, so that defecation and urination can occur between the legs from the top participate.
When 2 people use the same toilet at the same time. One person using the normal seating position on the bowl, and the other takes a seat on the top tank Upper Decker. Term originated at a warehouse in Holbrook, Long Island.
All the stalls but one were full, so me and Jose did BUNK BEDS in the only empty stall.