Proto G is a mechanical engineer showing his stuff in a simple but genius plan for managing prototyping wire for soldering--in your cheap mechanical pencil. Making a 3D printed gizmo that you will not find in any hardware store, Proto G allows you to keep your wire spooled up, neat, and literally at your fingertips. All you have to do is download his .stl files and pick up a few inexpensive items to make this cool contraption. Read more about the device in the full article: http://3dprint.com/88254/mechanical-pencil-prototyping/
Below is a photo of the prototyping pen in action: