A spinning wheel or Charkha is a device for spinning thread or yarn from natural or synthetic fibres. The spinning wheel replaced the earlier method of hand spinning with a spindle. Gandhiji was very keen on improving the Charkha technologically in order to improve its productivity. While he was lodged in Yeravda Jail, Gandhiji himself worked on a portable design of the Charkha which could be easily carried anywhere. A set of two stamps were issued which depicts the two kinds of Charkhas used by Mahatma Gandhi.