This is a code lock example, based on the Code Locks tutorial from RUST, archived on TWHL
here.
Punch in the four digit code, hit the yellow button and the door will open.
Wait, what's that? The code? What code? Oh! You mean the code for the door? I'm sorry, I can't give that to you right now. However, the code is hidden somewhere in the map, see if you can find it without looking at the jmf or .map. Instead, play the bsp file. Good luck.