a flat at each side of the stage to prevent the audience from seeing into the wings
<noun.artifact>
Tormentor \Tor*ment"or\, n. 1. One who, or that which, torments; one who inflicts penal anguish or tortures. --Jer. Taylor.
Thoughts, my tormentors, armed with deadly stings. --Milton.
2. (Agric.) An implement for reducing a stiff soil, resembling a harrow, but running upon wheels. --Hebert.
To put me in my place, my chief tormentor, a boy who could become enraged by my use of precise English, snatched my unacceptable cap from my head and threw it on the tracks as we waited for the train.