[1] Typically, a kate consists of a standing rack with multiple rods which allow the bobbins placed on them to spin.
Tensioned kates have a band that loops over the bobbins to prevent them from spinning freely.
Some spinning wheels have built-in kates, although these tend to be more cumbersome to use than free-standing ones.
Electricians use a similar device to mount their spools of wire for pulling and storage.
An improvised kate can be created out of a cardboard box pierced by some sort of dowels.