A pin and groove assembly that keeps a tool in the unset position while running and then can be worked or "Jayed" to operate the tool. Common in retrievable packers and liner hangers
George E. King Engineering, 5000 Oilfield Terms: A Glossary of Petroleum Engineering Terms, Abbreviations and Acronyms, US 2010. http://gekengineering.com/Downloads/Free_Downloads /Glossary_of_Petroleum_Engineering_Terms_25_August _2010.pdf, (Oil - Amer) {593}