I am sure the other knots people are posting work well, but most people will never remember them. I suggest a surgeon's knot. It does the job well enough and is

I am sure the other knots people are posting work well, but most people will never remember them. I suggest a surgeon's knot. It does the job well enough and is simple enough that anyone can use it. https://en.m.wikipedia.org/wiki/Surgeons_knot https://en.m.wikipedia.org/wiki/Surgeons_knot