NPC's and ladders

How can I make an NPC use a ladder, in episode 2? It’s the func_usableladder entity. :s

I never saw any npc’s climb a ladder in ep2. But if you need one i think you have to make a separate mod with a custom sequence and a custom animation.

Not massively worried about animations and shit, I just want them to slide down a shaft.

I don’t think they have an animation to look like they hold onto the ladder and slide down.
If you want them to move down the shaft you can make them stand on a func_movelinear and make it invisible.