How can we make terrain like this

[scvn80]

http://tcx.xgm.ru/files/?TcX1.03.w3x
They make doodad like bridge and they can go under, above it.
I don't understand why they can do that

 

[xshadowyx]

I believe its called pathing, getting a pathing file on the object and allowing to be walkable on. After this you can walk over it like a normal bridge, and also walk under it...Like a normal bridge.

Theres some good tutorials on this.

Also im unclear about what you said since my Editor cannot open the file you attached.

 

[Nudl9]

I believe its triggered...

 

[scvn80]

They use other system. When I place a peon and remove it's trigger, these bridge won't work. That is what I found