Abstract: A modular magnet writing instrument and hobby tool comprises a plurality of permanent magnet segments and a writing cartridge. Each magnet segment is magnetized axially. An aperture extends longitudinally through the entirety of each magnet segment. The writing cartridge has an elongate body, which is sized for coaxial insertion within a magnet segment, or plurality of magnet segments, such that the magnet segments are in sliding engagement with the elongate body. In operation, different combinations of magnet segments can be axially positioned on the elongate body, in a variety of like-pole and unlike-pole interactions, to produce a plurality of writing and hobby tool configurations.