They were mostly used by smaller Navy vessels to alert sailors of a boarding attempt or other emergency. Battle Rattles were made of oak or other hardwoods and when turned or spun on the handle, made a loud repetitive machine-gun-like sound which was a call to General Quarters for all members of the crew. There were two models or types of battle rattle, a large two-handled one affixed to and located on the main deck and smaller ones used by individual sailors designated to sound the alarm (such as this one).
Battle Rattles were used by most of the world's navies but predominantly today are ones found that were used by the British and American navies during the 19th century. Most all battle rattles were made with a combination of screws and wooden pegs or dowels holding everything in place, and to be easily disassembled to make repairs when needed. As you can imagine no matter how well made these battle rattles would only last so long due to the impact made by the cogged wheel being drawn over and hit by the stiff wooden flapper.
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