Designed this to adjust the distance of hanged things without cutting or knotting a thread / String / Kite-Line Whatever. Used this for adjustable desktop-ventilators.

2x M3x6mm Screws
2x M3 Hex-Nuts

Wrap the line one time around the screw and tighten it a bit. After the remaining cord is rolled up (around the model), you can do the same with the second screw.