Creating Footprints/pathing

[Delcius]

How do I make a doodad with no footprint (my example being the Ulaan Destructible Bridge) capable of having a unit go across it? It apparently isn't capable of actually being used as a bridge. I've just placed some temporary pathing across using the ground pathing tool, but the unit just falls through the bridge to the next cliff level along the new pathing. Is there anything I can do to correct this?

I've also tried to play with the footprints a little but it seems like nothing changes when I mod current ones. Or when creating my own it actually has no footprint or pathing.