What are decorative cams?

Question

I found a very cute metal tin at the op shop with 'decorative cams' printed on the lid. The tin is about the size of three slices of bread stacked one upon the other. Inside it I found about twenty circular plastic things (the 'decorative cams'?) resting in metal slots which look like they would attach to something - perhaps a sewing machine?

What are they, and how are they used?

Answer 1

Sure, like this:
http://cgi.ebay.com/Elna-Cam-Style-01_W0QQitemZ330039175218QQcmdZViewItem