At the beginning of any row, thread a contrasting thread or dental floss through your lifeline hole and work the next row according to your pattern instructions. Remove the dental floss from the cable connector and continue to knit in pattern, leaving your lifeline inserted in this row. Now if you need to unravel your knitting, the lifeline will catch your stitches and keep them from unraveling further.
Insert additional lifelines throughout the project. If you are comfortable doing so, remove the earliest lifelines and reuse the thread or floss.
Should you drop a stitch or need to rip out a row or rows, the lifeline will keep your stitches from unraveling further and you can use it to help pick up the stitches and return them to your needles.
17.5″ cable makes a 24″ needle
25.5″ cable makes a 32″ needle
33.5″ cable makes a 40″ needle
17.5″ cable makes a 26″ needle
25.5″ cable makes a 34″ needle
33.5″ cable makes a 42″ needle