"Kör perçinli jumper" näme aňladýar?

Perçin bökýän kellesiniň kör bolmagy: perçin dyrnak kellesini dolamaýandygy sebäpli, perçin kellesiniň bökmegine sebäp bolar.

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