Sorry for late reply. Anyway, I like challenges like this. They make you think. In old threads there has been quizzes of what 3, 4, 5, 10 , 12 etc knots would be best to know, easiest for a knotting beginner to learn, most useful in general, most useful in certain situations (whaling doesn't come to mind, for some reason), but now you ask about what single knot to know. Ok, I just pretend it is about knowing just one single knot, and what that would be.
I started by trying to figure out any kind of scenario where one could know just one single knot, and I came to the conclusion that it could only be a science fiction scenario. So I wrote a little SF story to help make the challenge of picking ONE single knot more plausible. Here it is with my apologies for bad writing, language or sense of humour.
One day, long ago, when I was taking Fifi, our family giraffe, out for a walk, Fifi started to act nervous about something, so I followed her gaze and quickly found out that she had been frightened by a UFO in the shape of an alien spaceship. While I was calming her down the flying saucer landed in a clearing ahead, and without any delay one of its crew approached. "Twine?" he said. I recognized my nom de plume from the online forum of the International Guild of Knot Tiers (IGKT for short), and said the first thing that came to mind: "This is about knots, isn't it?"
"O, Twine" the robotic visitor from another planet said, "My planet, the planet of robotic aliens, has suffered a disaster, and you are the only one who can help us!"
"I'll see what I can do" I said, "but are you sure I'm the right person to ask? I don't know much about anything besides knots."
"That's exactly why we sought you out. Our mental scanners found you to be the most knowledgeable knot tier in the world, at least among those who didn't wear tin foil hats at the time of the scanning. Such hats block our mind rays."
That made me wonder, since I never thought that such hats were all that common among IGKT forum posters, but you live and learn, as I tell myself every time I make a mistake.
"My people, the robotic aliens from the planet of robotic aliens, are robotic, as you may have figured out already", the shiny chrome giant said apologetically.
"Yes?" was my reply.
"Well, we robo-aliens all work together guided by a supercomputer in the sky, and now its database has sprung a leak in the department of knots and knotting, so now we don't even know a half hitch from a quarter hitch. Will you save our planet by letting us absorb all your knowledge of knotting, hitching, bending, netmaking and so on?"
"If it doesn't take too long or is otherwise inconvenient", I answered.
"It may be a bit inconvenient, perhaps," the metal monster admitted, "because the knowledge we need to absorb from your mind will be eradicated from your brain due to the special emergency process we will have to use in this planet-threatening emergency. We were unable to untie the box that contains the manual for doing it non-destructively, as it was sealed by some kind of knot mechanism, and we, like I said, have lost all knowledge pertaining to knots".
"I see", I said, "but it would be too terrible for me if I didn't have the knowledge of tying and untying as much as a single knot. Maybe you should ask someone else."
"THERE IS NO TIME!" cried the metallic alien. "YOU ARE KILLING AN ENTIRE PLANET WITH YOUR EGOISM!"
I tried to explain to the mechanical miracle of technology that to each and every human his own pleasure and convenience is far more valuable than any number of planets, his own included, but he argued against that with such emphasis that poor Fifi (the giraffe I introduced at the beginning of the story to indicate its fictitious nature) dropped dead on the spot and I myself almost lost my temper. In short, the robot threatened to kill me there and then, but to soften my plight (in its own opinion, anyway) it said that I could choose to withhold ONE (1) knot from the memory extraction ray.
First I thought I should retain knowledge of the figure of nine knot, since that was what I was studying most intensely at the time. It is very useful both as a stopper knot (easy to open as soon as tension stops) a knot for tying mountaineers ropes together (probably even more secure than the EDK) and as the smallest possible version of a timber hitch. So it could be used as a stopper, a bend and a hitch, and it could be used instead of the figure 8 when forming a fixed eye on the end of a rope. I was fairly certain it would make for a good midline loop too, thus working as a replacement for the alpine butterfly loop.
However, I decided in favour of the slipped surgeons knot. It has only one advantage over the figure 9, but that was crucial to me. Without it (or some inferior version) I wouldn't be able to tie my shoes. People would say: There goes Twine, once an excellent tier of knots, but now he can't even tie his shoelaces together.
And there you have it. Forced to choose a single knot, it would have to be something to tie my shoelaces. I can't figure out how to do that using the figure of nine knot. I'd be grateful for any ideas of how to achieve the tying of shoes using only figure 9 knots.
