Quickie Professional Acid Brush
Not sure what it is really used for but I was looking for something to brush off some old plaster while doing my bathroom and this seemed ideal.
The picture shows it is wooden but the one in store is black plastic. Found them hidden away on a low shelf near the sweeping brushes.
Stiff, natural tampico fibres resist harsh acids. Wood block. Use with appropriate chemicals to remove marks and stains on masonry. Use with any standard threaded handle.
Might be useful also to scrub decking in the spring?