US Patent 11064767 Fastening device

A fastening device including a case unit and a spool is provided. The case unit includes a wall forming a receiving space, an upper opening communicated with the receiving space, and a lower opening opposite to the upper opening and communicated with the receiving space. The spool is within the receiving space. The spool is limited by the wall, and the wall prohibits the spool from leaving the receiving space from the upper opening.