An alternative to darning sock heels &amp; toes. Knit leg, &amp; top of foot only in whatever yarns you like. Then knit heel, sole &amp; toe with yr sturdy sock yarn. Kitchener stitch toe &amp; top of foot together. Preferably use a different coloured yarn to stitch side seams. When the need arises, unpick seam &amp; reknit heel &amp; sole. The top sock is on its 3rd incarnation!