Use a needle size that will give you a tight weave, so food doesn't leak through.
cast on 36 stitches. This is for a small bib - adjust the amount for a larger one.
rows 1, 3, 5, 7 & 9: knit
rows 2,4,6.8 & 10: knit, adding one stitch at the second stitch and the next to the last stitch.
knit until bib forms a square, then decrease two stitches every other row, the same way you increased at the bottom, until you are back to 36 stitches.
On the next row, knit 1/3 of the way in (in this case, 12 stitches), cast off the middle 1/3 of the stitches, and knit the last third.
On next row, continue to decrease until you have 1 stitch. Transfer the stitch to a crochet hook and crochet a single chain tie, stopping when the tie reaches 10 inches. cut yarn and weave excess yarn into tie with a yarn needle.
Knit the remaining side the same way.