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If you drop a stitch only one row down, it’s not necessary to use a crochet hook to fix it. Dropped stitches look like rungs on a ladder.

Use the right-hand needle to pick up the loop of the stitch where it is one row down.
Place it on the left hand needle.

Pull the “rung” or strand of yarn from the current row through the stitch on the needle, letting the other strand drop down over it.

This loop you’ve just created is now the actual stitch from your current row.
Knit as usual.