Jacobs Ladder — A series of horizontal panels held together with a vinyl bank. These panels flip to expose the opposite side when top horizontal panel is mechanically turned.

Jewel Light — Colored plastic or glass insert used in front of light source in panel faces to identify, pinpoint, etc., areas.

Jig — Shop or bench setup for making repetitive assemblies.

Jigging — Special dividers, sectioning and protective padding inside exhibit crates.

Jigsaw — Narrow blade set in a frame used with a vertical motion for cutting along wavy or irregular lines.

Job Foreman — One who is in charge of specific projects.

Johnson Bar — Long-handled wooden pry bar with metal tip and wheels used in freight handling. Also known as a J-bar.

Jointing — Technique of rendering lumber surfaces perfectly straight and smooth so as to permit a perfect fit. This operation is usually performed on continuous automatic machine called a Jointer.

Jones Plug — Theatrical term for multi-prong electrical disconnect.

Journeyman — Worker who has satisfactorily completed an apprenticeship in a skilled trade.

Junction Box ––Approved enclosure where electrical splices are made.

Jurisdiction 1. The jobs that may be performed by a specific labor union. 2. The locality where a contractual dispute is decided.