filter problem

i have a B&W 72mm circular polarizer filter that fell apart today. (i guess i pulled it apart, but i'm blaming it on the dog!) seems the snap ring that fastens the filter to it's mount came out. i can usually figure stuff out, but it looks like it takes an engineering marvel to put this ring in to assemble it. anyone got any ideas how to accomplish this?

thanks

Harold,
This happened to me while on the Oregon coast last week (I was on the beach). Mine was a Hoya circular polarizer. So if yours is similar it might help. Put the retainer ring on the piece that came out (the retainer goes on the outside of the piece). Then the trick is to slide this into the part that screws onto the camera. If you go in square, the retainer ring blocks it. But put the piece in slanted, with the split part out and opposite the split in the split ring going in first. Seat the ring on that one side then push the other side in. Worked for me.

hi roger. thanks!! i fixed it. not an easy task!!