Page 222 - Buck Tilton - Outward Bound Ropes, Knots, and Hitches 2 ed.

Attach the loop to the main rope with a girth
hitch (see page 81), keeping the hitch loose.

Credited to Dr. Karl Prusik, circa 1931, the prusik knot can

be tied with one hand, a useful skill in an emergency when
the other hand may be unavailable. The word “prusik” may

be used to refer not only to the knot but also to the loop of
cord in which the knot is tied and to the ascending

technique: “to prusik.” Many climbers today utilize
mechanical ascenders instead of the prusik knot.
Mechanical ascenders damage a rope more than the prusik,

but the prusik will fail (slip) if it is overloaded, a problem
rarely seen with mechanical devices. This knot might be

used in camping for such tasks as hanging bags on ropes
suspended vertically to keep the bags out of animal reach.