Im getting this from another forum so im guna copy and paste it
Works off pressure applied to nose, chin, cheek, and poll. The shank works similarly to the curb bit, the longer the more pressure etc. Need a chin strap to function properly. Reins attach to the shanks.
Does not have shanks, and the reins join at the bottom. Applies pressure to nose and chin. Apparently they help the horse pull their nose in and break at the poll more effectively.
There is a danger with hurting a horse with any bit, if handled wrong. If the hackamore is fitted properly, sitting on his nose right, and the curb tighted to the proper length, it is no more severe than any other bit in the wrong hands. The hack is no different than any shank bit, work with gradual, light, pressure. Don't jerk on a hackmore, any more than you would jerk on any other bit. If your horse is light and willing to please, the hackamore may very well be a nice choice. If you have a friend who owns a hack, it may be a good idea to borrow it and see how Harley responds to/ likes it.
I ride a mechanical hackamore, as does most of my barn. All the riding academy horses ride hackamore with loose curbs on the trail, to prevent people from hauling on them, We have eight year old children ride the academy horses with the hacks, and have never had a broken nose or any other injury to the horse in 20 odd years.The only thing I have noticed switching from a full cheek to a mechanical hack is having to pull out (plow rein) more on turning, from the different point in the pressure. It's just a matter of Hoover needing to learn the new pressure, and what I'm asking. I like the hackamore, Hoover responds well to it and seems to enjoy riding more in it than his old full cheek. To me, and what I have been taught, is that the mechanical hackamore is just another form of bit, and is no more severe than any other if used properly.