Behind the tormentors is a curtain called the “olio,” which fulfills the triple purpose of hiding the rest of the stage, serving as scenery for acts in One and often as a curtain to raise and lower on acts playing in the space back of One.
Five, or six, or even seven feet behind the tormentors you have noticed another set of wings which—extending parallel with the tormentors—serve to mask the rest of stage. The space between these wings and the line of the olio is called “Two.”
In Two, acts such as flirtation-acts—a man and a woman playing lover-like scenes—which use scenery or small “props,” and all other turns requiring but a small playing space, are staged.
An equal number of feet back of the wings that bound Two, are wings that serve as boundaries for “Three.”
In Three, playlets that require but shallow sets, and other acts that need not more than twelve feet for presentation, are played.
4. Four or Full Stage
Behind the wings that bound Three are another pair of wings, set an equal number of feet back, which serve as the boundaries of “Four.” But, as there are rarely more than four entrances on any stage, Four is usually called “Full Stage.”
In Full Stage are presented all acts such as acrobatic acts, animal turns, musical comedies, playlets and other pretentious acts that require deep sets and a wide playing space.
5. Bare Stage
Sometimes the very point of a playlet depends upon showing not the conventional stage, as it is commonly seen, but the real stage as it is, unset with scenery; therefore sometimes the entire stage is used as the playing stage, and then in the vernacular it is called “Bare Stage.” 
 The New Leader, written by Aaron Hoffman and played for so many years by Sam Mann & Company, is an excellent example of a Bare Stage act.
On the opposite page is a diagram of the stage of Keith’s Palace Theatre, New York City. A comparison of the preceding definitions with this diagram should give a clear understanding of the vaudeville playing stage.
At audience-right—or stage-left—flat against the extended wall of the proscenium arch in the First Entrance (to One) there is usually a signal-board equipped with push buttons presided over by the stage-manager. The stage-manager is the autocrat behind the scenes. His duty is to see that the program is run smoothly without the slightest hitch or wait between acts and to raise and lower the olio, or to signal the act-curtain up or down, on cues. 
 A cue is a certain word or action regarded as the signal for some other speech or action by another actor, or the signal for the lights to change or a bell to ring or something to happen during the course of a dramatic entertainment.