Fence rub. You could try a braid running down the length of his neck. This would give his neck a nice clean look. You may need to practice this to get a nice tight braid without it looking too bulky. Even try it while sitting on his back. When I showed english we used to braid a bazillion braids along the neck then fold it underneath and stitch in place. Elastics could break. This produced a nice tidy look. If you try this, always do an odd number. The look is something like the western banding. What kind of tree is the horse tied to? Interesting bark.