In addition to signaling that the scene is ending and that a new scene is about to begin (since there were no curtains and no real sets to speak of—more modern ways of alerting the audience that the scene is changing), the rhyming couplets at the end of the scenes in Shakespeare's plays often sum up the scene or alert the audience as to what might be coming next. For example, at the end of Act 1, scene 1, the Weird Sisters say,

Fair is foul, and foul is fair;
Hover through the fog and filthy air. (1.1.12-13)

This clues us in that they are up to something bad: they are going to make fair things seem foul and foul things seem fair (or good seem bad and bad seem good); further, they plan to "hover" nearby and, perhaps, wait to learn useful information. Their paradox helps us to understand that they are tricky and deceptive and not to be trusted. Even the repeated "f" sound in these lines (called alliteration) makes them sound breathy and snakelike and slick.

At the end of Act 1, scene 7, just after Macbeth has recommitted to the plan to murder Duncan, he says,

Away, and mock the time with fairest show.
False face must hide what the false heart doth know. (1.7.94-95)

This couplet reinforces Macbeth's renewed promise to his wife regarding their terrible plot. He is committed, now, to deceiving everyone into believing that he is still a good and loyal servant of the king when really, his false face hides what is truly in his heart. Notice, too, that he repeats the alliteration of the "f" sound that the Weird Sisters used previously; this is a subtle indicator of his own commitment to deception and evil. As the final lines of the scene, they have a moment longer to resonate with the audience and, perhaps, subconsciously, allow audience members to note the connection.

Shakespeare's theater had no curtains to close or lights to dim as most modern theaters do to indicate the end of a scene. His plays in the Globe were performed in daylight on a stage that jutted out into the audience.

He used rhyming couplets to signal the end of a scene, and his audiences were remarkably good listeners to hear the rhyme. The remainder of the play was typically written in blank verse, which is unrhymed; as a result, the rhyme would be more apparent. Even so, we have to admire the Elizabethans for their acute hearing and concentration.

At the end of Act 2, scene 3, Malcolm says to his brother:

But shift away: there's warrant in that theft
Which steals itself, when there's no mercy left.