I have a requirement where I want to tie a knot with the two ends of a cord where the length of the loop can be adjusted using either of the ends. (The knot has to be present on both the ends of the cord)
I want to use this to hang my compass/whistle (or any other smaller objects) around my neck while I go outdoors. While fixing the length of the cord would work in most of the cases, using an adjustable knot allows for the cord to be used by multiple people without retying or using a different length cord.