Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:6283872.

Well on my car, the seal in the door came loose, which was annoying. Gluing it back on only helped for a few weeks.

So to attach the both loose ends of the seal I made this little fastener to stick inside to assist the glue by reducing downward force. (Even holds without the glue)

Just print two of those, interlock the two and stick it in the seal. Just be careful, that the door is not damaged if the plastic part doesn't fit too well.