This method allows you to remove the original cast on row in order to pick up and use the live stitches at a later time. Particularly handy for adding a decorative border, or for increasing the length of a sweater that is knit from the bottom up. You will need a crochet hook and a length of yarn in a contrasting color for this technique.
Crocheted Provisional Cast On
Begin by placing a slip knot on the crochet hook in the contrasting yarn.
Wrap the yarn around the back of the crochet hook and across the front.
Use the hook to draw a loop through the original slip knot. You have now made one chain. (Holding onto the yarn tail with your right hand can make this easier to do.)
Continue to repeat this motion until you have made as many chains as you need in your cast on row. You may want to make a few extra, just in case. When you are done making your chains, cut your yarn and draw it loosely through the loop that was on your crochet hook.
If you hold the chain in your hands, you will see a ridge of bumps running along one side. These bumps are what you will use to pick up your first row of knit stitches.
Insert your knitting needle tip into the first bump.
Wrap your yarn around the needle and pull up a loop to pick up one stitch.
Continue to insert your tip into the bumps along the crochet chain and pick up stitches until you have picked up the number of stitches you need in your cast on row.
When you are ready (or when your pattern indicates you should) you can return to the cast on edge and remove your crochet chain. In an earlier step we threaded the end of the constrasting yarn through the last crochet loop. Undo this step to prepare for the chain removal.
Gently pull the contrasting yarn to remove the crocheted chain. This will reveal a set of live knit stitches. Insert your needle into these stitches and you are ready to begin knitting downward.