p>I discovered this join type when trying to make autojoining railings for
a game. Graphically it made no sense for a railing to continue into a set
of stairs if the staircase was going down; I wanted the railing to have a
nice post at the end instead. So I created a rule for this: If the stairs
next to this tile go down, count the corner tiles next to the stairs as
connected.</p>

<p>This join type is useful for realistic liquid, terrain, or cavern walls.
The incomplete corners "anticipate" a curve, so you