Lightning Catchers are mechanical items that are used to harness lightning and convert it to items. It is a retextured Redstone Repeater. It is crafted with the same recipe as the Redstone Repeater, but instead, the redstone is replaced with sunstones.
Lightning Catchers only work when in a thunderstorm. When one is placed, lightning that strikes has a 12% higher chance to strike the Lightning Catcher. If the bolt does strike it, the Lightning Catcher will light up and (if there is an adjacent Thunderchest) will store it. If there is no nearby Thunderchest, then the lightning (item) is dropped on the ground. The item is a Lightning Fragment. The easier way to obtain Lightning Fragments in a Creative server is to use "/lighting" on a Lightning Catcher, or simply select them out of the Creative Inventory. There is usually 3-7 Lightning Fragments created when a bolt strikes this item.