The bottle sling's specific form allows it to grip a cylinder, assuming it has even a slight flare or collar, and lift it along its axis when the knot is loaded by all four strands.
[2][3] Knot expert Cyrus L. Day believed the bottle sling was not described again in print until Craigin's 1884 A Boy's Workshop,[4][5] although Clifford Ashley noted it was illustrated in Johann Röding's 1795 Allgemeines Wörterbuch der Marine ("General Dictionary of the Navy").
As the name suggests, the primary use for this knot is to suspend bottles, jugs, and other items with similar shapes.
Looping the running ends through the bight and tying them together will make a sling that grips and can be used to lift the bottle.
[6] This provides a convenient method of lowering a beverage bottle from a boat into the water to chill.
As mentioned above, the knot is believed to have been used medically in ancient Greece for applying traction in the reduction of fractures and dislocations.