cause i can't be stuffed making tuts..
and your are wrong
let's take a wall
you will want the character to be able to walk right next to it
setting it to X will keep you away
setting directions right left and down (if the wall is upper) will allow you to look as if you walk close to the wall, since up is blocked you won't be able to cross the wall
and so on, but that might be a bad example for most walls as they are more often than not seen in "upper view" which requires a full X
and then there is priorities basicly they are like the layers but not quite
they will allow the npc to walk under or above the hero and so on and so on
meh.. play with it a bit..