One way of doing it is making the "func_door", then going into its properties, select the do not render option if you plan on not showing the brush and just the entity. Then select a "prop_dynamic" entity followed by a door model that has the ending "_dynamic" in it. Then you can make a brush surrounding the door itself with a brush with the trigger texture and make it a "trigger_multiple" for the door so players within that area make it open or close. (make sure you have named all these things before continuing) Once you have all that out in your map go into the properties of the trigger, go to the "outputs" tab and select "add" then going down the boxes enter the following. In "my output named" select "OnStartTouchAll" then in the next box labeled "target entites named" enter the name of your "func_door" you want to link it to. Then in the box "via this input" select or enter "open" and disregard the other 2 boxes. To make the doors close, click the "add" button again to make a new set of commands and go down the boxes again with these commands instead: "OnEndTouchAll", "Your func_door name again" and "close". Now for the funcdoor you will be doing something similar, Once you are in the "outputs" tab for your funcdoor follow the same procedure as before but this time enter the following commands: "OnOpen" "Your door prop_dynamic name" "Set Animation" this time in the "with parameter override of" box, enter "open". Finally, click "add" one more time and do it again except this time anything with open in the last output just change to close for this one. So its "OnClose" "your func door" "Set Animation" "close". That's pretty much how to make a basic door...dont worry once you put this all into practice, it will be quicker than you think! Also, if you want to make a team specific door there will be a few more hoops to jump through, but first crawl before you walk. Hope this helps you out!
