Wat betsjut blinde klinknageljumper?

Blinde klinknagel springkop: om't de klinknagel de nagelkop net wikkelt, sil it de klinknagel springkop feroarsaakje.

https://www.yukerivet.com/news/the-core-of-the-blind-rivet-is-not-completely-pulled-out-what-is-the-reason-for-the-fracture/