The edge of any map tile and the entire area of any partial hex along the edge are considered walls unless they are covered by a corridor tile. Doors are also considered walls when they are closed. Where the edge of a complete hex on a map tile comes up right to the edge of the tile, there is a dark border to remind you that a wall exists at that edge, though it does not technically begin (for cases of line-of-sight) until the edge. If two map tiles are set next to each other such that these dark edges line up (i.e. the border of the first and second room of the first scenario), the wall is considered to still be there as a one-dimensional line.