Learn a munter hitch, it's extremely versatile and can do everything from securing something, to belaying or rappeling off it (with a locking carabiner). It is

Learn a munter hitch, it's extremely versatile and can do everything from securing something, to belaying or rappeling off it (with a locking carabiner). It is an extremely important knot for setting up rescue systems as it can hold a load under tension, yet can be undone and slack added to the system while under complete control.