Well we always knew that J was going to be a difficult one and it has proved to be so.
We hope there are one or two that you didn’t know.
Not sure that K next time is going to be a lot better so roll on L and M

JACK- a triangular brace hinged to the floor or other piece of a set tto support it from behind

JAMB - The side post or basically the lining of a doorway or other opening in a set wall

JOG - a narrow flat or piece of wood attached at right angles to another flat so that it adds a bit of variety and interest to the
otherwise straight walls of a box set

JUKEBOX MUSICAL - A stage musical show like Mamma Mia or We Will Rock You that has been constructed from pre-released existing
songs, usually from one artist or genre.

JULIET BALCONY - A high level platform in a theatre or on a stage set designed to look like the balcony scene in Romeo and Juliet. 

JUTE - A natural fibre used to make hessian cloth, sackcloth similar cloth. 

JUVENILE LEAD - The most significant role in a play or film that is performed by a young actor.