Because nearly all of my casting practice is on grass I have had to develop a way to roll cast on grass, close anchor and a biggish D loop. All fine and dandy for grass. However it does lead to some bad habits that have to be sorted out whenever water becomes involved and the grass style just won’t do if you are going to be tested. You can have a much shallower D loop and the anchor can be a lot further away on water. The rod can also be a lot more upright, which is what an examiner would want to see. This is because the anchor will stick where it is placed as the fly, leader and line will be gripped by the surface of the water so that the tension created by the stroke isn’t lost. On grass, the moment you begin the forward stroke the tag slips.
I have pondered this problem and come up with a piece of equipment that not only solves the anchor problem but also requires you to be accurate, so you get two for the price of one.