This is a type of anchor knot, or bend, used to attach a rope to a ring or a pole. The knot stays tied when the rope is slack, and stays firm when tension is applied. It's easy to tie, and easy to untie.
Take rope in hand with a foot or so spare. Wrap the rope twice around the fixture, then take the end of the rope and feed it back through the loops. Finish with a half hitch.
| . |
____ | . |
\ . \ | . |
\ . \ | . |
\ . \ | . |
) . ) | . |
______|_._|_| . |__
/ . . . . . .| . |. \
/ . __________| . | . \
/ . / ) . )| . |\ . \
/ . / / . / | . | \ . \
/ . / / . / | . | ) . )
/ . / / . /___|___|_/ . /
/ . / / . . . . . . . . /
/ . / \________________/
/ . / _____________| . |____
/ . / / . . . . . . | . | . \
/ . / / . ___________| . |__ . \
/ . / / . / _______ | . | \ . \
/ . / / . / / . . \| . | \ . \
/ . / / . / / . ___ . | . | ) . )
/ . / / . / / . / \ .| . | / . /
\ . \_ / . /___/ . /___ /__|___|__/ . /
\ . / . /. ./ . / . . . . . . . . /
\_ / . /___/ . /__________________/
x( . /xxx/ . /XXXXXXXXXXXXXXXx
XX| . \XX/ . /XXXXXXXXXXXXXXXXXx
xXXX \ . \( . ( / . / / . / XXXx
xXXX \ . \\ . \___/_._/_/ . / XXXx
xXXX \ . \\ . . . . . . / XXXx
xXX \ . \\_____________/ XXx
XXXx \ . \__/ . / xXXX
XXXx \ . . . / xXXX
XXXx \______/ xXXX
XXXx xXXX
XXXx xXXX
XXXx xXXX
XXXx xXXX
xXXXXXxxxxxXXXXXx
XXXXXXXXXX
Thanks go to tkil's write-up on Drawing knots with ASCII art, for the inspiration to try drawing one.