Red-Lined tile Deletion

How do I delete the unwalkable area's marked by a red-lined tile because this has ofter befuddled me

 

They are two kinds for tile blockers - putted by you (light red tiles), and given by game engine (pregenerated for larger objects, i.e. trains, ships) (dark red tiles). Putted tile blockers can be simply removed from Edit menu (go to Edit, push "TB" button,. and click on existing tile blocker).
Pregenerated tile blockers cannot be removed, however you can simply put on it any other "walkable" tile (i.e dirt, grass, street surface, whatever).

 

I just tried both of those and the walkable tiles like gravel and grass did not work. The "TB" only made it light up brighter. Any more ideas?

 

HA nevermind. I just looked at it again and when I pressed "W"" then I noticed 2 flag things that were hidden behind the wall. But thanks because this will help me in the future.

 

If it's an object-based light red tile, rather than a facade or environment tile (like deep water), you can right click on the object, go to flags, and but a check mar in the "no block" category