Names and faces to bikes

Push a flat head screwdriver into the gap, twist and it to open up the open end of the clip.. it will then ping off and fly far away so as never to be found.. or... hit you in the eye.. one or the other. Once removed from your eye just snap it back on the same way..

I find my fingernail, or (HTFU) a pair of pliers works better:

http://bicycletutor.com/quick-release-chain-link/