I am guessing its some way of popping ( rivet style) the female "capture" end into the frame, allowing you to screw a nut into it, so in effect, making a "screwable rivet ??????
As Alex (Collie) says absolutely spot on, they are brilliant, you can buy a tool, from about £16-65 or if only using a few then there is a DIY bodge solution you could use, I'll find the link if you're interested.