When I was young I had a whiteboard in my room to plan out the month. When I was young and did not use an agenda yet this worked great. Over the years I started using an agenda and stopped using this whiteboard to plan. I still used the whiteboard to write small things or to pin down papers that I wanted to keep for a while.
But the whiteboard did not look so good anymore because some of the black lines scratched of but not everywhere. So I decided to take of all the lines.
This was a lot easier than I thougth. I started using a knife but quickly found out that it made scratches where I did not want them. So I tried some soap with sand in it. Which also did not work.
As a last idea I used a brillo pad which worked perfectly. It did not make scratches but got rid of the unwanted lines.
And it worked perfectly.