Butt soldering wire holder.

thingiverse

This tool holds wires end-to-end as you solder them together. They employ magnets to stick themselves onto a metal work surface, applying gentle clamping pressure in the process. It closes down on the wire like a clamshell, with the foam exerting light pressure, secured by tiny springs inside. The handle makes it effortless to open the lid of the tool. Instructions Print two copies. You won't need any additional help, really. Print the "handle" at an angle. Use a thin 1/8" or 3mm rod for the small connections -- you might have to drill out the holes to get a smooth fit in the end. Use a medium 1/4" or 6mm rod for the main pivot point. Again, drilling is optional but it will help with the assembly. Secure the bases in position using two screws on the hinge rod. Attach the handle to the lid using 1/16" thin wire or a finishing nail. Affix four magnets to each base and two to each cover of the tool. The small recesses are sized specifically for 12mm x 1mm round magnets, remember? Install a square section of low-density foam into the inside of the lid, keeping it snugly in place. If the foam is too thick or rigid, it might interfere with the lid snapping shut and holding properly. This writer discovered the right combination after testing several types, including that thin packing material from electronics packaging, only to find the perfect balance for this task at hand.