You can make a hat by joining circular needles properly.
When making a hat, socks or a sweater, it is often helpful to use circular knitting needles to knit in the round. Although using circular needles can make your project easier, there can be difficulties. One of the difficulties in knitting in the round is joining the two sides together without causing the knitting to become twisted. There are ways to prevent twisting from happening when you knit on circular needles.
Things You'll Need
Cast on your stitches onto circular knitting needles as you would for straight knitting needles.
Hold the circular needles out in front of you with one hand.
Use your other hand to adjust the stitches so they are all facing the same way.
Hold the needles as you normally would when knitting.
Knit the first stitch while keeping your pinkies on the stitches on either needle to secure them in place.
Knit as usual. The stitches will remain as they should in order to create a circular knitting project.