When I knit the baby bib for my niece, I had to knit an I cord for the ties of the bib.
This is how to knit an I cord.
1) With two double pointed needles, cast on a few stitches. For the baby bib 3 stitches were used.
2) Knit all the stitches.
3) Without turning your work, switch the needles so the needle with the stitches are in your left hand.
4) Slide the stitches to the right hand side of the left needle. Pull the yarn tight across the back of the stitches, and knit the row.
Continue steps 3 and 4 until the desired length of tie that you want for your bib.
That's it. So very simple to make ties for your baby bib.