I chipped the hell out of mine, was glad I had not paid to have them powdercoated or would have been livid!
Pull each side out, and then push the square part forward as there is a small tab underneath, then to put the R one on, put the tab in, then prize the clips into place, they have quite a bit of give, but be careful of fingers, as they slap pretty hard and painful if they come back at you.