Delta Outpost (Underground Safezone Monument) 4.0.0

In the video, it shows the author placing a piece of sewer tunnel, then he clicks on a spot on the monument, then goes and clicks on a spot on the tunnel and a green line appears. The two parts then connect seamlessly. How is this done?

Saw you comment on discord, but I'll repost it on here if anyone was wondering and didn't see my response. In rust edit there are things called sockets (top right) of menu's and you can enable them. Clicking and dragging to other sockets will snap certain prefabs into place. Ex is caves, tunnels, sewers, pipes to name a few off the top of my head.

Also pertaining to this monument specifically I recently updated it so sockets are not really needed as much now that it's got a dedicated surface and more along the lines of a traditional monument. That said feel free to modify it to existing tunnels if those who bought it want too.  

Sounds awesome. I do plan on buying this tomorrow when I am going to work on the map for the next wipe.