The compartments are intended to be filled with a substance such as sand, and incorporate...http://www.google.com/patents/US5332185?utm_source=gb-gplus-sharePatent US5332185 - Gun restAdvanced Patent SearchPublication numberUS5332185 APublication typeGrantApplication numberUS 08/071,757Publication dateJul 26, 1994Filing dateJun 8, 1993Priority dateJun 8, 1993Fee statusLapsedPublication number07175