I was told that the most important thing for a rigger was to have strong hands, strong enough to tear the canopy or stitching during the pull test if it was compromised.
Ken wrote:
The paragraph above that mentions "not many non-destructive tests available" jibes with what they have discussed regarding canopy life. The FAA has no calendar limit but a common guideline is the "pull test". If the canopy fabric tears, you flunk and you also now have a hole in the fabric. Note that the pdf below also references the "thumb test", likely an old-timer technique of pressing a calibrated finger against a taut panel and seeing if it punctures the weave.
https://www.pia.com/wp-content/uploads/TS-108.1.pdf