Provisional cast on is a great technique for knitting projects that require you to join two parts of your work later on. It allows you to easily remove the provisional cast on and place stitches on a needle, making it a useful technique for projects like scarves, shawls, sleeves, and collars.
What you need:
- crochet hook to match knitting needle.
- Acrylic or other slippy yarn in a contrasting colour
- Knitting needles and project yarn
HOW TO KNIT THE PROVISIONAL CAST-ON
Using the slippy contrast yarn, create a slip knot and put it on a crochet hook the same size as your intended knitting needles, being careful not to make it too tight. 
Place working yarn behind the knitting needle. 
Pull working yarn through slip stitch. 
Bring working yarn behind knitting needle. 
continue to bring working yarn under needle as you you form a chain around the knitting needle. 
When the number of stitches required are on the needle, chain a few extra stitches before breaking and finishing yarn.
When you are ready to unzip the chain and pick up the stitches there will be one less stitch. This is caused by how the stitches are formed.When working in the opposite direction from a provisional cast on the stitches are off set by half a stitch.