Co-operative map editing lets you build and modify maps with others easily. This mode allows you to edit maps online with other players who could help speed up repetitive or boring tasks, bring in fresh ideas or spot errors you may have missed.
To start co-operative map editing, when in a server, type: /mode 1 and then type: /map and then your mapnames name and press ENTER. You will have to of made a "newmap" previous to entering the server to be able to co-op edit it.
You will then need to send the map. You can do this by typing: /sendmap and then your mapnames name and press ENTER. Note: Custom materials can't be sent, they will have to be downloaded another way if you are using them. If you are using a custom "cfg" file, it will automatically be sent with the map, if there is a cfg file present.
Note: Some useful editing commands can't be used in co-op editing, such as: copy, paste, slope, arch, undo, etc.