There are a few methods to use when knitting the crown of a hat. Most hats are worked in the round on circular needles. However, as you get close to the top of the hat, working the decreases, the hat becomes too tight to continue using circular needles.
There are a few options you can use. This option is to use 2 circular needles to work the decrease of the hat. You will need 2 different circular needles, length doesn’t matter. Use the circular needle you used to knit the hat, and get another circular needle that is the same size, but not necessarily the same length. You can continue knitting with these two needles.
This video shows you how to use these 2 circular needles to work the crown.
This is one method to knit the crown. I have two other tutorials showing two different methods to work the crown. Choose the method that works best for you!