It is in One that monologues, most "single acts"—that is, acts presented by one person—and many "two-acts"—acts requiring but two people—are played.
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.
2. Two
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.
3. Three
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."