I concur with Mark. In fact, my co-judge and I failed a dog because the handler was worrying enough about the line to the mark that we turned to each other and wondered if the man thought the bird was a blind. I would guess the chap spent about 90 seconds assuring a perfect line to the mark. I now feel as though he felt the dog had not seen the fall and so was trying to pull off a bit of magic. I say this because I have a dog that is near-sighted (proven by Auburn Vet School) and we've tried this a time or two in training.