Removing Walls from a Tilemap

How do you remove walls from a tilemap? Right click removes the tile, but if it was marked as a wall (red highlight) this remains and I can’t find any obvious way of removing the wall highlight.

Thanks for help

Click the wall button and then use the erase tool to erase the walls

Aha!
I see how you can draw lines/rectangles of walls too.
Thanks for speedy response.