Film term:
This is a wooden box, often helpful on the set to raise up equipment, for the cameraperson to stand on if the tripod is up very high etc. Often you will find them used as seats by the less involved participants. There are also half apples and quarter apples, which as you might expect, are half and one quarter as thick respectively
Glossary of Film Terms - http://homepage.newschool.edu/~schlemoj/film_courses/glossary_of_film_terms/
reprinted with permission