You can tighten or loosen it as needed. The wrapped part permits the cord to slide nicely, tightening and loosening as you wish. I would recommend a silken cord and not the one illustrated, which would be too scratchy.

(That really is the second knot I learned to tie. And you should have seen the nuns react when one of them walked into a classroom full of second graders who where tying them into the window shade strings. You can only imagine!)