Što znači slijepi premosnik zakovice?

Glava skakanja slijepe zakovice: budući da zakovica ne obavija glavu čavla, uzrokovat će skakanje glave zakovice.

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