A lifeline can save your knitting and your sanity! They're generally used when knitting lace in case you need to rip out errors. Before putting one in, make sure there are no errors so far in your knitting. You'll be using the lifeline to stop the stitches laddering down any further when you rip out, and to help you replace your stitches on the needles. Be sure to mark your chart or written instructions so you remember where you've put it in! You can put multiple lifelines in if you like, or just one or two.
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