Crochet stitches are so varied and knotted, I'm often at a loss for fixing a torn thrifted blanket or handmade sweater.
But now I've found some tutorials for repairs. Should I say I'm hooked and I want my fix? Probably not.
Repair a crocheted blanket
Repair a granny square afghan
Another mend a granny square tutorial
Mending the center of a granny square
Mending crocheted lace
Mending a tarn rug
Not technically a repair for crocheted or knitted items, but this explanation for how to weave in yarn ends will make all those projects look better.