CHAIN in BDSM: 
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The power of Chain:

The Great Chain (at Trophy Point)

Links forming the Great Chain stretched across the Hudson River at West Point during the Revolutionary War and served as a key element in the area defenses. Used from 1778 to 1782, the 500-yard chain floated on logs and was designed to act as a barrier to enemy ships. This was the second of two chains to be placed across the Hudson. The first was placed four miles below West Point between Fort Montgomery and Anthony's Nose, near the location of the present-day Bear Mountain Bridge.