The Granny knot is one of the three Reef knot twins; the only difference is that the lines cross in opposite directions. The Granny knot is very insecure. It can easily slip along a line, and this feature allows it to turn effortlessly into a double half hitch — a hitch, very useful in boating.
ABoK #3, #80, #186, #464, #1206, #1405, #2553, #3786
Fold the rope to form an open loop with the running end upside.
Thread the 2nd rope through the loop and under the 1st standing part.
Pass the 2nd running end over the 1st standing part and then under the 1st running end.
Pass over the 1st running end and through the loop.
Tighten the knot.
The Granny knot is complete.