Page 51 - Buck Tilton - Outward Bound Ropes, Knots, and Hitches 2 ed.
P. 51
CAMPING KNOTS: Bends
Square (Reef) Knot
A QUICK AND SIMPLE BEND FOR TYING TOGETHER
TWO ROPES OR CORDS OF EQUAL DIAMETER
This fundamental knot, known to many as the square knot,
is more accurately called the reef knot. It is used for binding
two pieces of cordage of equal diameter or two ends of the
same piece of cordage. If improperly tied, as it often is, it
becomes the infamous and highly insecure granny knot.
Even tied correctly, the square knot loosens easily and
should not be used as a bend where security is required.
Knot tyers involved in many different pursuits use this one.