A provisional cast-on is a type of cast on that is created using waste yarn that can be easily removed to reveal live stitches.
It can be very useful if you want to later knit in the opposite direction (as for scarves and stoles when you want to make both ends of the piece identical, for example), or whenever live stitches might be preferable to a cast-on. In my About Town skirt pattern I use a provisional cast-on to create a knitted in elastic waistband casing. In my Adalida Cardigan pattern, I use a provisional cast on to knit a curved lower edge across all the main pieces after they have been sewn.
There are many methods for creating a provisional cast, you may find you have a favorite that you use all the time, or you may vary them according to project or whim! The Crochet Provisional Cast-on Follows::