"....The Grackle Noseband, named after the 1931 Grand National winner who wore one, has the lower straps fastened under the bit and the top one above, with, in the original pattern, a connection at the rear to keep them in place. The nose pressure is consequently localised higher up the face and can be considered as being less restrictive to the breathing than the usual drop noseband and it will also allow a little more movement in the jaws. It will, nonetheless, prevent an evasion of the bit by the jaws being crossed. Properly made, the small nosepiece, through which the two intersecting straps are passed, can be adjusted up or down to increase or decrease the strength of the action. In recent years, the Grackle has been called the 'Figure 8' or 'crossover noseband'...."
This extract is take from 'Saddlery' by Elwyn Hartley Edwards, a world authority on the subject of saddlery and bitting.
I thought this explained the Grackle Noseband very well . I am not eloquent enough to explain it in my own words too well !
Obviously I know all my nosebands (and make them) and understand their uses, but I'm a saddler, not an author, so thanks Elwyn !
(Sorry for the 'book' - Blame Elwyn!)