Leading Screen?no clickage

I've noticed some maps have the neat attribute that you don't have to click/press any key to start.. They just start when they are finished

(I mean this when you use a loading screen with text etc, not just all players and a minimap)

Does anyone know how to imitate this attribute? It would be a great thing to add to any map! so that you can have a briefing and people won't have to click. o_O

The only way I know to do that is to not use a custom loading screen

Allright.. but if you're NOT using a custom loading screen.. then how can you just start the map without having to press a key first..?

A custom loading screen I meant.

And closed for thread necromancery