Lower the currently selected frame so that it disappears under any frame that overlaps it. If multiple frames are selected they are all lowered in turn.
Gostwng y ffrâm a ddewisir yn gyfredol er mwyn iddi ddiflannu dan unrhyw ffrâm sy' n gorgyffwrdd â hi. Os dewisir fframiau lluosol, cânt eu codi i gyd yn eu tro.