A fishing swivel is a small item made of metal. It is used to keep lines from tangling.
Fishing swivels come in different sizes ranging from (UK measurements) 1.0 (smallest) to 4.0 (largest).
Swivels are also used in the construction of kites and poi, again to keep the lines from tangling.
A fishing swivel
/----\
/ /--\ \
\ |__| / --Metal hoop.
\ /
\ /
__||__
| _||_ |
| |||| | --Small barrel connected to metal hoop.
| ---- |
| | --Large barrel containing the two small barrels.
| ____ |
| |||| |
| -||- | --Small barrel connected to metal hoop.
|__||__|
||
/ \
/ __ \
/ | | \
\ \__/ / --Metal hoop.
\____/