As the parts are very small, this sanding block may be difficult to print. I used ABS with 0.05mm layers and a 0.4mm nozzle (on a Prusa i3 mk2s printer). The handle is constituted of two identical parts which wrap the needle and the sanding paper extremity. A rear cap and a sliding ring allow to lock the handles together. Pay attention to the ring mounting as it is flared for a better locking.