Commands to assist the reuse of boxes (set up by \sbox or by the lrbox environment); the \settobox... commands behave similarly to the \settowidth (etc.) commands. For example:

      \newsavebox{\mybox}
      \newlength{\mylength}
      \sbox{\mybox}{Hello World}
      \settoboxwidth{\mylength}{\mybox}
    

The author is Heiko Oberdiek. The package is Copyright © 2000,2006,2008 Heiko Oberdiek.