This stitch can be used either decoratively or to conceal mistakes. It is made on top of the knitted sweater with yarn and a tapestry needle. A size 18-22 rounded tip needle is best to use so that the needle slips more easily through the stitches without splitting the yarn.
Bring the needle from the back of the sweater piece to the front through the base of the stitch to be covered. Then insert the needle from the right to left behind the stitch directly above.
Insert the needle from front to back into the base of the stitch to be covered. Do not pull the yarn too tight. Try to keep the stitch the same size (tension) as the surrounding stitches.