*passe-partout*

‖ n. [ F., from passer to pass + partout everywhere. ] 1. That by which one can pass anywhere; a safe-conduct. [ Obs. ] Dryden. [ 1913 Webster ]

2. A master key; a latchkey. [ wns=1 ] [ 1913 Webster ]

3. A light picture frame or mat of cardboard, wood, or the like, usually put between the picture and the glass, and sometimes serving for several pictures. [ 1913 Webster ]

4. A strip of adhesive paper or gummed tape used to mount a picture between a piece of glass and a backing. [ wns=2 ] [ WordNet 1.5 ]

5. The method of mounting a picture between a piece of glass and a backing, using a passe-partout{ 4 }. [ PJC ]