how to hide fabric/clothes gaps and junctions on walls?

hi. this is my firs post here... i'm wondering how do the pros do this: the insulate walls with rockwool (or similar) and over it they use fabric. it seems they "push" the pannels into the wall because i can't see screws or pins. how do you do this? sorry for my poor english... ps: this is my littles studio... http://www.altramusica.net/docs/recording-studio, if you want to suggest me some improvements. happy new year! luca