Gold filled linking hook to a chain or rows of beads. 
 
Imagine this scene; you have this 1970's long string of beads, unused in your collection, but yes! would be perfect with your outfit, what can I do?
With a linking hook you can double your string of beads and transform it into a 2 layers necklace, if still too long, just twist it.
Done, ready to go...
 
Size: 11 mm x 9 mm