I needed to secure a patio door and used a 3/8" bolt into a T nut pushed into the patio door and hidden underneath the existing hardware door lock plate (see photo). The only problem with my fix was I needed to leave a wrench by the door in case of emergency. By 3D printing a knob and pushing the bolt through it I could easily open and close the door when needed which in winter is not at all. It is nice that the bolt pulls the door against the weatherstripping making a nice tight seal.
I've been transitioning to Fusion360 but I knew what was needed for this knob and wanted a quick fix instead of a learning experience. I also saved the time and $4 not going to Lowes. I'll get back to F360 soon.
-Version 2 has a slightly tapered head with the ribs cut back. Due to some misalignment of the door the first knob was rubbing on the frame, this one won't rub. This version has a slight misalignment and will require some sanding to get the bolt to fit, recommend printing Version 3 instead.
-Version 3 was rebuilt once it was noticed version 2 was slightly off center.
This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/kQtuDzh7Lbh
Infill seems low for a structural part but with all the curves and walls it's mostly solid where you need it. Sometimes solid isn't stronger.