These can be used to secure the ends of slits in plastics and cloth. If you are adding a slice, vent, expansion accordion or similar and need to keep it from splitting further when under stress. Punch on the end of the slit/split. It creates a very durable stop without a stitch, patch or grommet. It will not suffice in areas of extreme tension.
If doing this on harder plastics, where slits can run away quickly, punch the holes first and cut the slit from one hole to the other. If done with a score first, followed by a full cut, the split will follow the score to the other hole if it tries to run away. Not guaranteed, of course, so practice.