The spinning of yarn, either from wool or flax, was something that housewives (with the help of their children) had to do if they needed things such as new clothes or any other cloth items. Yarn simply was not easily available to be bought; you had to make your own if you wanted it.
There is a mistaken idea that the early settlers wove their own cloth from the yarn they had spun. Very few actual settlers had the room for a loom, nor did they have the time to spend weaving, which was time and energy exhausting.
In actuality, the homesteading families spun their own yarn, which was then taken to a professional weaver to have the cloth woven. But before the yarn was taken to the weaver, it needed to be measured. That is where the clock reel came in.
The reason this piece of equipment is called a clock reel is because it contains a group of gears, similar to a clock, which allow it to measure the number of turns made by the arms. The arm assembly was attached to a gear, whose teeth were interconnected to another gear. That other gear had one tooth that was a slight bit longer than the rest. The purpose of the one longer tooth was to push against a slender piece of wood, called a 'weasel'. The weasel would be bent out of line and as the longer tooth pushed past it, the weasel would snap back in place, at the same time smacking against a stationary block of wood attached to the inside wall of the clock reel, making a 'click' sound. For that reason, this reel was also sometimes called a click reel. From the point that the weasel snapped against the wall to make a 'click' until the next time that it 'clicked', a certain length of yarn would be wound around the clock reel's arms.
The clock reel shown in the photo above has an 'around the arms' circumference of 90 inches. From one 'click' to another it takes 120 turns. The 120 turns measure 10,800 inches / 900 feet / 300 yards. Different sources give the length of a skein anywhere from 500 to 1200 feet (it depends on the thickness and weight of the yarn). The homesteading housewife would find out from the local weaver how many feet of yarn he required in a skein, and measure it accordingly.
Clock reels, as noted above, were sometimes called click reels because of the clicking sound they made. They also were sometimes called cleck reels, for the same reason. The name given to this piece of equipment, by people who aren't aware of their 'historic' or 'traditional' names, is simply yarn winder. They are sometimes, mistakenly, called swifts or niddy noddys, but those are other pieces of equipment which look quite different from the clock reel.
I can't leave this subject without mentioned the children's nursery rhyme Pop Goes The Weasel. The nursery rhyme refers to the 'weasel' of the clock reel snapping back into place, and making a 'popping' sound. The wording of the rhyme vary from region to region. The version that I was told when I was young was:
All around the cobler's house;
The monkey chased the weasel;
The monkey stopped to pull up his socks;
Pop! goes the weasel.
It is also claimed by some that the children's nursery rhyme Hickory Dickory Dock referred to the clock reel.
Hickory dickory dock;
The mouse ran up the clock;
The clock struck one, the mouse came down;
Hickory dickory dock.
The 'clock' striking one was the clock reel's weasel snapping back into place.