Door Problem
Okay, I'm making a map. (obviously)
But there's a problem with doors.
It doesn't like the left door, it thinks my button output is invalid.
Output is:
OnClose door_left Close
Close is invalid.
Any ideas? Please help.
Gonna need more information than this. Is "door_left" a func_door, func_door_rotating, prop_door_rotating?
func_door
I also have the same problem with opening it. The right door opens just fine.
So just delete the left door and copy/paste the right door, rotate it and change the names. Make sure to change the name and the parent if you are using a model.
also, don't forget to change the open direction 
Wait a minute... can you explain that in a different way?
Right now, it sounds like I'm supposed to have 2 door_right entities.
Step 1. Copy all parts of the right door (brush, model, anything that moves or is a part of that single door)
Step 2: Rename all the parts of the newly copied door to be door_left, etc. Be sure to also update any parent names and move direction.
Step 3. Cut a hole in the box
Step 4. Put your junk in that box
That's the way you do it!
But it doesn't look like the door is the problem. Really, it's the button.
The func_door that is closed to activate the button doesn't like the output Close for some reason.
But if the RIGHT one works, copying it will make the NEW one work. I'm guessing you just didn't have the parent set to the correct model for the left door. Just copy and past the door, rename the stuff and copy/rename the output on the button. It's not that hard, just do it.