...two horizontal criss-cross wraps underneath, from front to back, hold the hackle fibers in place long enough to apply some glue. ZapAGap in this case. But it could have been almost anything. Water based fabric cement. UV glue or even head cement. Zelon is (by far) the easiest hackle material to work with, but hare's ear, hare's foot, fox mask or even ground squirrel (picket pin) can be made to work.