I bought a PBF gas mask and an L1 NBC suit last year for a photo project. It got a bit delayed, so now it's finally time to use them together for the first time (I don't know if the PBF and L1 were ever used together, but they were the most badass combo I could find

). But I can't quite figure out how to fasten the straps on the L1...
I'm fairly certain the small end of the button goes into the small stretchy holes on the straps, but how then do you attach it on the receiving end? Does anyone know?
Thanks in advance!
Attaching photos since I'm not sure I'm explaining it clearly: