For my pathfinding system I wanted to make it compatable with directional blocking and no cutting corners so I came up with a few procs to help with that. The the core of the directional blocking system is from Lummox Jr but everything else is from me. You may think these are pointless, but they come in handy if you want to just check if something can be entered in general, not just with a specific mob.
See the procs at
http://bwicki.byond.com/ByondBwicki.dmb?DrumerslExamples