Spray Pattern Indicator
See where you have sprayed our moss and weed killers with a temporary blue dye additive. All you need to do is add this marker to your spraying solution and spray as normal. It will leave a faint blue stain on the surface to show you where you have sprayed. DON'T WORRY, the stain is only faint and it fades over a very short period of time so you will not be left with a blue patio or lawn.
Adding this to your solution will save you from spraying over the same area more than once or missing areas completely.