From appropriate parallel waves or lines, or eight chain thru: Circulate, ½ (Half) Circulate. The center 4 (those in the wave) Hinge and those centers facing in Cross. Meanwhile, the ends Turn Thru or Left Turn Thru as appropriate. From most places (e.g., waves) this ends in lines back to back. It can be done from anywhere the Circulate, ½ (Half) Circulate gives a definite center wave.

"Percolate But" means the Hinge and Cross is replaced by the “But” call. The ends complete the call as usual.