In which of the Gerber files shall I put my dimension layer ?
I’ve always included it in the top (and bottom) silkscreen. In a single board design I think it’s easy to guess that the big square is dimension… 
Question is how to do it when you have a multi-project panel…
Thanks for your reply, if I should ever order here, I will do it as you suggested. On the other hand, I have the feeling that nobody is willing to answer easy questions here. It took more than a year until sombody else answered my VERY DIFFICULT question 
???
maybe you didn’t ask it very clearly.
try to write it more clear, please 