The FFI definition:
lacks something in my opinion. Bernd has provided a great video that shows effectively hauling with the line attached to a stationary post in place of holding it with the line hand. Torsten has also pointed out that we can haul using our rod hand while holding our line hand totally still.Single haul/hauling – pulling on the fly line with the line hand while fly casting
Double haul – hauling on consecutive casts (back cast and forward cast)
Consider the following picture:
From our starting position A we can see that if we move both the rod and line hands together (B) during the casting stroke that we do not generate and movement of the line relative to the rod guides, i.e. this is a non-hauled cast. In all of the other scenarios (C, D, E) we have moved our rod and line hands apart by one unit (foot, meter, whatever unit of distance including miles for Vince who is a giant among men ). The difference in these scenarios that I will pull exactly the same amount of line through the guides by first using my line hand only, using both my line and rod hands and using my rod hand only.
My suggestion is that we define haul as relative movement between the line and rod hands during the casting stroke.
Note that this is separate from hauling distance and speed, which I intend to address separately under a different topic. It also has nothing to do with the efficiency or effectiveness of the haul, which is yet another topic. Biomechanics and teaching? More topics...