The rope tensioner is used to change the pedal angle of your Nordic Kayaks footrest or closed loop pedal system on other craft.
 
The more tension you put on the steering cable, the steeper (towards you) the pedals will be. This makes the steering/control of your surfski more sensitive. If you prefer it a little looser, take some tension off the steering cable by turning the cable tensioner so that the pedals are flatter (pointing away from you).
 
On the NK surf skis and kayaks, the cable tensioner is mounted between the two eyebolts that hold the guide rails of the footrest.