A theatrical device is a method or technique used onstage which has an aim or purpose. The aim when using the 'v' effect is to ensure that the audience are constantly reminded that they’re watching a piece of theatre.
Narration is used to remind the audience that what they’re watching is a presentation of a story. Sometimes the narrator will tell us what happens in the story before it has happened. This is a good way of making sure that we don’t become emotionally involved in the action to come as we already know the outcome.
Commenting upon a character as an actor is a clear way of reminding the audience of theatricality. For example, midway through a heightened scene the action might break for the actor to comment upon their character in the third person, ‘Darius felt his anger rise. He wasn’t being listened to and wanted revenge’, before returning to the scene.
This device was used by Brecht more frequently in rehearsal than performance. It helps distance the actor from the character they’re playing. It also reminds the audience that they’re watching a play and forces them to study the actions of a character in objective detail.
Speaking directly to the audience breaks the fourth wall and destroys any illusion of reality. An example would be the moment where Grusha pleads to save baby Michael in The Caucasian Chalk Circle by Brecht:
I brought him up, shall I also tear him to bits? I can’t.
A placard is a sign or additional piece of written information presented onstage. Using placards might be as simple as holding up a card or banner. Multimedia or a PowerPoint slideshow can also be used for this effect. The musical, Miss Saigon, for example, used a slideshow to demonstrate the loss of lives in the Vietnam War which was highly effective. What’s important is that the information doesn’t just comment upon the action but deepens our understanding of it.
For example, a married couple are arguing and the wife is very upset. If the actress held up a placard saying ‘I’m miserable’ that wouldn’t tell us anything about the character that we didn’t already know. However, if her placard said ‘I’m having an affair’ or ‘I’ve never loved him’ the audience would be forced to consider other aspects of their relationship and to think about deeper reasons behind her tears.