Do you have the Capture Product from Peak Design? If not, and you are curious, check out the FAQ's for more information.
Capture is a great product, and the capture-compatible (a.k.a. ARCA style) release plate makes TrailPix totally compatible with all of Peak Design's Capture designs. Just unclip your camera from the Capture clip on your pack or belt, and clip it securely to TrailPix.