You attach the button (with the red edge) to your camera and fasten the rectangular holder to your camera strap.
Simply slide the button into the holder for quick fastening.
Slide the button out for a quick release.
With this system you can remove the strap speedily when you want to set up on a tripod, or if you need to attach the strap to another camera - to which you will already have added two additional buttons.
I wouldn't be without mine - they save time, are totally secure and very strong.
You can order these directly from Peak Design -it is probably best to do so if you are in the States or in Europe. There are country choices on their web site.
Fasten the camera plate (manfrotto or arca) to the base of the camera. When you want your hands free but your camera at the ready, slip it onto the camera clip (which may be fastened to you belt). It will be held there securely by the 'capture' clip until you need it again.