There was a time when materials were costly, and time was plentiful. To get a pair of socks, you would need to get the wool off the sheep, prepare the wool, spin it into yarn, take that yarn and knit it... you get the idea. Nowadays, if you want a pair of socks, you can hop down to the shop to get any flavor of sock yarn. Or, you can just buy the socks themselves.
But when your materials are scarce, you want to conserve them in any way you can. That means unravelling and re-knitting sweaters as children grow older, or darning socks. Recently I had a mishap when my darning pile got mixed in with the laundry pile - my pair of merino cashmere socks were already wearing thin, and while they didn't felt in the wash, the thin spots got even thinner to the point where I just couldn't darn them any longer.
Instead, I'll make them into something new.
I started by snipping one stitch a few inches down from the top of the sock. I'll use those bits of ribbing later, rather than having to re-knit them. After picking out the snipped yarn from one round, the ribbing came apart from the rest of the sock and I set it aside.
The rest of the sock got ripped out. The yarn is quite a bit more fragile now than it started with, after years of wear. Some spots have felted together a little bit.
Note: be aware of what direction you were knitting. I knit my socks toe-up, so I unravelled towards the toe. If you knit your socks cuff-down, you could snip off the toe and unravel towards the top.
The yarn was too thin to use in some spots, and I had to cut out the darned sections as well. Between my two socks, I ended up with 35g of usable yarn, plus the intact cuffs.
The cashmere merino yarn is still luscious after all this time, supremely soft and warm. But, it isn't particularly sturdy, especially after several years of wear. Instead of fashioning new socks from them, I'm going to make them into a pair of soft warm legwarmers to keep my pale legs cozy.