We recommend adjusting the curb bit to have about two fingers between the chain and the horse's jaw. You should have about two fingers' space between the bridoon bit and the lower hooks.
The curb chain should lie flat and be adjusted so that when the reins are adjusted, the bit arms move to a 45° angle at most to the bridle straps.
The tighter the chain, the smaller the angle and the more severe the action will be. The looser the chain, the larger the angle, and the lighter the action.