Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:1428769.
A solder dispensing pen. Wrap some solder around a pencil, drop the coil of solder in the tube, thread it through the cap, and solder away! If your shirts have a front pocket, that's where the clip comes handy.
This thing was made with Tinkercad. Edit it here