Prompt corner

In a theatre, the prompt corner or prompt box is the place where the prompter —usually the stage manager in the US or deputy stage manager in the UK —stands in order to coordinate the performance and to remind performers of their lines when required. It is traditionally located at stage left. 

Effective prompting can be a challenge. The American prompter Philip Eisenberg recounted the story of a Maria Callas performance during which she needed louder prompts. The famed diva swooped down in a curtsy right in front of the prompter’s box and —mid-curtsy, unnoticed by the audience —gave the Italian command "più forte!" (louder) to her boxed colleague.