passe-partout
\ pas-pahr-TOO; Fr. pahs-par-TOO \ , noun;
1.something that passes everywhere or provides a universal means of passage.
2.a master key; skeleton key.
3.an ornamental mat for a picture.
4.a method of framing in which a piece of glass is placed over a picture and is affixed to a backing by means of adhesive strips of paper or other material pasted over the edges.
5.paper prepared for this purpose.
Quotes:
Sophie's little passe-partout enabled her to pass almost anywhere, and if it were shown or hinted at, to have effect in the interviewing of superior servants or of any other police officer.
-- Sir Harry Johnston, "The Veneerings" 1922
But with his remark about Vokt anyway he felt as safe as if he had a ticket or passe-partout in his pocket: he strutted up and down like a peacock for a few moments eyeing the assembly with disdain.
-- Wyndham Lewis, "Tarr" 1918
Origin:
Passe-partout comes from the French phrase of the same spelling which literally means "(it) passes everywhere."