olio drop

Another name for roll drop.

Sometimes also called an "Ad Drop" because often in vaudeville theatres, the drop was used as the backing for "in one" scenes and the theatre owner sold advertisements for local businesses, which were painted on the drop.

An excellent example, from a 1920's theatre in Illinois:

Theatre Pictures

From http://www.kbrianneel.com/slang.html :

Olio Acts - Vaudeville numbers that were performed between the between the acts of the principal show. In the early days of Vaudeville, specialty acts did their numbers in front of an oilcloth curtain while the stage was being set for the next part of the show. The word "olio" is Italian for oil. Also sometimes used to refer to the supporting acts in a vaudeville bill.

Olio curtain - Also called the "in-one curtain" or in today's lingo the "mid-stage traveller." In a vaudeville theatre the Olio curtain was set about ten feet back from the footlights. The olio curtain often had advertising painted on it.