Simplify the following text for a Grade 9 native English-speaking person.
Original: Circular knitting , which is done on circular or double-pointed needles , produces a seamless tube and is used to create things like hats , socks , mittens , and sleeves .
Simplified: Circular knitting is employed to create pieces that are circular or tube-shaped , such as hats , socks , mittens , and sleeves .