This is a headset / headphone hook that is able to clamp to a desk or shelf. The 3D print consists of the clamp which comes in two parts, a large bolt and a cap for the bolt. Once the two clamp pieces are printed, they slide together like in the pictures. 

the bolt is threaded in through the clamp and tighten to attach the clamp to the desk. 

the components should be printed at a layer height of 0.3mm max. A larger stack height may make the threads on the bolt too coarse and they may not work properly.