Falling debris...
Hi, I am relatively new to Hammer, but I have spent a long time now watching numerous tutorials and reading guides.
So I want to make an overgrown-theme map where the player walks into a trigger and the floor collapses under them and the player falls down. I've seen this in many Hammer maps and also the single-player campaign in the beginning where Wheatley tells you to find the portal gun and the floor collapses.
Nooby question I know, but I really want to improve my Hammer knowledge.
I would also like to know how to make the debris of the floor fall with you. There isn't any animation in the model browser that I've seen...thanks in advance. 
EDIT: And I hate my stupid rank on this site, I DO know what a brush is...God.
The entities you'll want are func_physbox, prop_physics[_override], and (if the objects are other entities already) phys_convert. I look forward to seeing your map!
Ok, so I put some prop_physics(s) (don't know the plural for that) and put their World Models as walkways from the props_bts folder, then I put them together to look like one walkway. Then I put a trigger on the walkway and connected the trigger to the walkway with the input "break", so when the player was crossing it it would collapse under them. But when I go into the map, the walkways aren't there.
What am I doing wrong?
EDIT: Ok, I changed all of them from prop_physics to prop_physics_multiplayer, and now they are visible in-game. But when I walk through the trigger they simply disappear without falling. Also, I can't stand on them, I just fall right through them...
You'll want a prop_physics_override or phys_convert for that, they're dynamic-only models. But in a4_destruction are some good dynamic walkways with cinematic collapsing animations that will look better.