Yarn swift

A swift holds a skein of yarn while it is being wound into a ball, so you don't have to fight it all the way.
If you're a hardcore knitter, you buy your yarn from hippy communes in faraway places, or you spin it yourself[1]. This gives you yarn in skeins - long loops that are good for dyeing, but non-trivial to knit with. To get it into a ball, you need someone or something to hold it and prevent tangles, while you do the winding by hand or with a ball winder. That's where the swift comes in: it holds a skein of yarn, and rotates gently on demand, allowing to you to unwind/rewind yarn as needed without requiring a large family to assist you.
The canonical example of a swift is the umbrella swift. Wikipedia has a picture: https://en.wikipedia.org/wiki/Swift_%28textiles%29 . We[2] wanted something similarly light, yet sturdy enough for the wildest of knitting parties.
The arms of the swift expand to the diameter required for the skein when you press the top disk downwards, at