Wood Bench - Blueprints How Do I Keep Sharpie Markers From Washing Off Of A Wood Bench Outside?

How do I keep Sharpie markers from washing off of a wood bench outside? - wood bench - blueprints

Some of my family is not a bank for my wonderful grandparents, with all the children and grandchildren on behalf of children on the bench with a Sharpie marker. I wonder whether there is a way to avoid too fast.