A hook that you can clip onto then end of a horizontal surface, such as a tabletop, bookshelf, etc. to hang things on. 
I'm using it for hanging a basket with filament on. I'm using Vik's Y-bearing holder to make sure that it can rotate (see http://www.thingiverse.com/thing:921 ). I put a loop of rope through the two holes that hang over this tabletop clip. 
Version 2.3 has some improvements, the hook's lowest point is now nearest to the table. A cord will tend to rest there causing minimum torque on the hook-clip. 
It is made stronger at the two 90 angles that have to withstand forces. This is a more efficient use of material and builds faster. 
A hole under the hook where no material is required for an adequate strength of the hook. 
Version 2.3_thin is simply for a thinner tabletop/shelf.