This is a captive nut backing plate designed to turn a standard M8 Nyloc into a captive fastener. You will need to bond the plate to whatever you are fastening it to using a suitable epoxy/glue or industrial double-sided foam tape such as a 3M VHB which I have done.
I design this fastener to secure a composite splitter/lip to my Lotus Elise so I am able to take it on and off without having to remove the front under tray. As the nuts are fixed to the inside of the clam you don't need to get access to them to remove the splitter and they stay in place. The design is super light, easy to install. It has a 60mm dia base to help spread the load more than a large washer would do.