Vertical Joint Box/ Dome Type Splice Closure, 24 Cores. It protects fiber optic splices while providing fast and easy no-cost re-entry. It can be installed on aerial, in manholes, ducts and mounted on poles. How to Splice Fiber Optic Cores in a 24 Core Joint Using a Fusion Splicer #fiberoptic #maintenance Learn how to properly splice fiber optic cores in a 24 cor. The 24 core configuration represents a significant advancement in splice closure. The box stores direct or derived splices, supporting up to 144 fibers housed inside through splice trays. It is made of tough chemical resistant engineering material which effectively prevents it from ageing caused by heat, cold, oxygen and UV radiation.