How to make a Wire Frame actor--I'm sure it's in the documentation but can't find the link to the documentation here and doing a search didn't help me:
On Add Actor---where it says "Normal" use the drop down menu. Gives you choices of Canvas, Wire Frame or Filled. Found it randomly. : )
What to use it for? Among other things, as a sensor to stop actions like the player's being able to jump to the skies, I hope. : )