Common Sense?

[chips]

It's marked Common Sense - S. B. Mfg Co Milwaukee WI.

[Lostmind]

Clothes line attachment?

[amecks]

With a name like "Common Sense" one would think the use would be obvious! 

A search finds other household type items with that brand name.  Corn husker, window sash pulley, rodent trap, flat iron.
There is a company Scovill that makes DOT brand "Common Sense" fasteners - grommet type click fasteners for canvas.  The history page on their website is interesting but does not mention the CS brand.
Maybe the piece in question is a tie off for venetian blind cords?