Fabrics are often sewn in a long narrow tube to allow a filler (such as cording) to be added inside the tube. To hide the stitching and the unfinished edge, the tube must be turned inside-out relative to the way it was sewn. That process is called tube turning.  Fabric may be turned with a common item such as a chopstick, or with tools such as the Fasturn, Loop Turners, or Hemostats.
Stiffer fabrics and narrower tubes are more difficult to turn than softer fabrics and broader tubes.