In lighting design, a working sectional is a drawing that shows the sectional angle for a lighting instrument. It is used to determine its trim height.

This type of drawing is used to help select the instrument size used. After a working sectional for a specific instrument has been drawn, the apex of the template is placed at the specified trim height for that instrument. This drawing helps to make sure that the appropriately sized instrument will have a field angle that slightly overlaps the lighting area and a maximum throw distance that is longer than the required throw distance.

This method of instrument selection, however, is suggested only as a general guide. The designer needs to make instrument selections based on what is aesthetically appropriate for the particular situation, in final analysis.

A working sectional is NOT the same thing as a lighting section.