Hi all, this is a 3D printed version of an extremely impressive machinist's trick where a bolt is given both left and right handed threads which enabl...es two nuts (one RH one LH) to ride on it concurrently. Idea being that one motion (in this case the rotation of the bolt) produces two equal and opposite translations on each of the nuts. I think it's a really cool toy and one that works pretty well! Depending on how well your 3D printer is calibrated, you may need to scale the bolt down 2% in slicer to ensure a decent fit. Thank you for printing!