Alien Swarm Climbing

How do I get aliens to climb on the walls / ceiling? Is there a tool texture or something?

I need to know also.

Try making a ladder across the whole wall, and see if you can make it exclusive to the aliens?

[editline]11:17PM[/editline]

Don’t forget to put nodes on the walls then

Check the included vmf for the sewers, I think they do it in that map right?