An inefficient way to keep flats vertical is to use a picture-frame-like brace called a jack.

Name: An inefficient way to keep flats vertical is to use a picture-frame-like brace called a jack.
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Quizplus · Accepted Answer

A jack, or more specifically a "flat jack" in theatrical terms, is actually an efficient way to keep flats vertical. It is designed to support and stabilize flats (scenery pieces) on stage, acting as a brace to keep them upright and prevent them from tipping over.

An Inefficient Way to Keep Flats Vertical Is to Use