Tree Jack : A grooved saddle of wood or metal rollers contained within two steel plates, attached to a tree with a strap, used as a guide for skyline, sail guy, or similar static line. It is also formed to prevent a shard bend in the line
US Department of Labor, Logging eTool: Glossary, Occupational Safety & Health Administration OSHA, Washington, D.C., USA 2010. https://www.osha.gov/SLTC/etools/logging/glossary. html, (OSHA/ Logging - Amer) {620}