Safety Harnesses Tethers and Jacklines | West Marine What They DoIsaf RequirementsJackline ConsiderationsTether ConsiderationsSafety harnesses are webbing assemblies that physically connect you to the boat to prevent you from falling overboard or, failing in that role, are intended to keep you from being separated from the boat. Harnesses are either stand-alone items or are integrated with offshore type inflatable life vests. Tethers clip you to a fixed-location padeye or to jacklines (also called trolley lines or jack stays) that are lengths of rope, webbing or wire running fore and aft or athwartships. Jacklines c..See more on westmarine life jacket harness | eBay Find great deals on eBay for life jacket harness. Shop with confidence. Skip to main content. eBay Logo: Shop by category. Speedo UV50 Kid's Life Jacket Age 4-6 Front Zip Safety Harness Swim Vest VGC. Pre-Owned. $8. Guaranteed by Mon, Jul. 15. Buy It Now +$6 shipping.