Decals: Creating your own [Tips]

[Numerius]

It is very useful, thank you.
But I have a question regarding creating decals. How do I make my decal to stick? I mean... When I view it through the level editor it appear at the place where I put it, but in the map viewer it is not showing + when I reload the map in the level editor id also disappears (but if I click on the place where it was it still shows me the area, but it is empty). I would appreciate your help!