This technique is a crochet provisional cast on. The basic idea is that you knit your first row into a crochet chain, which when you are ready, you can unzip this chain to leave you with live stitches.
Abbreviations:
WY – waste yarn
RS – right side
YOH – yarn over hook
Crochet Cast On (with waste yarn)
With WY, make a chain that is several chains longer than the number of stitches to be cast on; cut the yarn and pull the end through the last chain. It is helpful to put a knot in the yarn tail at the beginning of the chain. You are going to pick up through the loop on the BACK of the chain stitches. With the chain RS down, the loop looks like it is holding the two chains together. Begin a couple of chains in from the end and go into the loop from front to back with your needle and use it to bring yarn through as you would to knit a stitch. Continue until you have the correct number of stitches on your needle. Remove WY. When the stitches have been grafted or put on needles, undo the last chain (this will be the end without the knot). Pull on this end and “unzip” the chain. Should your “zip” stick, clip the WY and undo it then pull again.
Provisional Crochet Cast On (with waste yarn in base of wrapped loops)
Note: Working with a larger needle will insure that the provisional loops can be picked up easily later on.
With working yarn make a slip knot and put it onto crochet hook. Hold yarn tail and WY in left hand with needle. *Hold the WY behind the needle and with the crochet hook in the right hand and in front of needle, YOH and pull through loop on crochet hook. Use left hand to bring WY behind needle. Rep from * for the correct number of stitches. Tie a knot in beg yarn tail.
Crochet Provisional Cast On (around the needle)
Note: Working with a larger needle will ensure that the provisional loops can be picked up easily later on.
With WY make a slip knot and put it onto crochet hook. Hold yarn tail and WY in left hand with needle. * Hold the WY behind the needle and with the crochet hook in the right hand and in front of needle, YOH and pull through loop on crochet hook. Use left hand to bring WY behind needle. Rep from * for the correct number of stitches. Cut yarn and pull through last st. Tie a knot in beg yarn tail. When the stitches have been grafted or put on needles, undo the last chain (this will be the end without the knot). Pull on this end and “unzip” the chain. Should your “zip” stick, clip the WY and undo it and then pull again.
Around Needle Provisional Cast On
Using WY, crochet hook, and needle of appropriate size, put a slip knot onto crochet hook. 1) Hold the yarn and needle in left hand, with yarn behind needle. *Using crochet hook in right hand, *YOH and pull through loop on hook. 2) Move yarn behind needle and rep from * until there is 1 stitch less than the total on needle. Put loop on hook onto needle.