Rudder raise/lower cords are used on most trailing rudders and some skegs (in that case it would be a single Skeg Raising cord)
Some kayak rudders are self deploying (spring loaded) and use a single cord used to raise the rudder they will have a cleat to secure the cord in position
More typically the raise lower is controlled by a cord/s that pulls the rudder in either direction.
This can be done as two separate cords potentially with one on each side of the kayak or both on the same side. More commonly it is done as a closed system (loop) with the balls placed so that pulling the rear toggle forward changes the rudder from one location to the other.
This loop is often made from 3mm Cord between the rudder and the toggle with a short length of shock cord (4 mm is common) attached between the two toggles and through a deck saddle or pulley (to reduce friction) allowing the rudder and cords to move freely.
Models that we stock that use a toggle ball include the Mission Eco Bezhig, Mission Contour Double, Surge Sit on tops like the Viper 12 Bass 10 Pro, Fusion 10
Also this is used on Surge Ultra Light sit inside kayaks to control the seat back rest trim (back and fowards) as well as the under thigh support position (up and down)