The slip knot is a stopper knot that can be loosened quickly by pulling on the bitter end to remove the loop. (Knots with a similar motif are referred to as slipped knots.)
Tie a slip knot in the end of a string, twine or thin rope when you need to untie the stopper knot quickly, such as when cinching a load under pressure that is firmed down with multiple half hitches. The knot won’t slip easily, especially when wet.
A. & B. Start with an overhand loop, and pull a short bight of the bitter end through the loop.
C. Leave enough bitter end protruding from the knot for you to pull when you want to release the knot.
D. You can use the slip knot as a quick stopper for a line passed through a grommet in a sail, tarpaulin or boat cover.
Original materials used with thanks to Irene Rodriguez and John Bennett