This is a tool that helps to make the rivets I use in my glasses. The tool slides over the handle of those cheap snippers that probably came with your Ender 3. Slide until the hole is under the snipper blade. Place a length of filament through the hole until it hits the shelf at the bottom. Make a cut and a perfect length of filament should fall away. Repeat for as many rivets as you need. Then take the cut pieces and form the rivet heads using a soldering iron at 200C. Place the rivet through the arms of the glasses and form the other end. See the pictures for details.

This tool will print without supports on its side. There is one section of bridging that any printer should be able to handle. The slot has a longer and shorter side. Print with the short side up to minimize the bridge. See the pre-sliced G-code below.