It's a common technique that directors have employed in film since the beginnings of it.
They used it quite often with Stewart and Sirtis during TNG. Getting a tight two-shot with either of them and Frakes sometimes required some help.
"I need an apple/half apple here' - supposedly, wooden apple boxes had been used for the purpose at one time. There were usually boxes of various heights on hand, to be used for different actors or shots.
Supposedly, the director of Stolen Holiday had a long shallow ramp constructed so that Claude Rains could enter a room and cross to stand face-to-face with Kay Francis.
Nowadays they're often called "Cruise boxes." But not in front of the actor. Or so i've heard.