A provision in specific types of indentures which grants the issuer the right to retire twice as many bonds as initially determined under a sinking fund requirement. With this option, the issuer can make additional retirements at or close to par. This would particularly be in the best interest of an issuer at times when interest rates drop to low levels. In contrast, a doubling option doesn’t serve holders of indentures as it deprives them from receiving potential above-market interest rates.