First, it’s important to note how they’re the same. On kayaks, rudders and skegs are both used as tracking aids in currents and windy conditions to help keep the kayak heading on an intended course. With that in mind, the short answer for how they are different is as follows: rudders are mounted externally and turn the kayak to keep it on course, and skegs are mounted internally and adjust the kayak’s hydrodynamic properties to neutralize the effect of wind and currents.  Check out this great article from our friends at paddling.com that discusses the benefits and drawbacks of choosing a skeg and rudder system. We also discuss the rudder vs skeg question here on our blog