This 3D model was designed with Fusion 360 and is a hat stretcher, it can also be multifunctional, it can be used to adjust hats that are too small or to maintain the shape of a hat. The project consists of three arms that act as guides (be careful not to unscrew them too much or you'll have to re-insert them by hand each time), then there's the adjustment pin that acts on the two threads, and then there are two U-shapes with integrated threaded screws, one with a clockwise screwing direction and one with a counterclockwise screwing direction, so that with the movement of the adjustment pin, the movement of the two shapes is simultaneous regardless of whether you want to separate the two shapes or join them. I included two versions in the project, one with 3 arms and one with 2 arms, choose the one you find most useful. I calculated that the maximum opening to prevent the guides from coming out is approximately 55 mm. The installation is as follows: insert the three guides into one shape, screw the pin a few mm and then screw the other shape to the pin, also a few mm, then interact with the pin, decreasing the distance of the two shapes until the guides touch the other piece. Insert the 3 guides manually and then interact with the pin again, bringing the two shapes to touch. If you can't screw the two shapes to the pin, it's simply because you're inserting them from the wrong side =)