They are not really necessary. They are used to tighten the string (between the footrest and the rudder) so that there is enough tension on the toe piece so that it pulls it forwards. See the attached video showing how to use it.
If the wheels on your kayak trolley become flat quickly, please check and rotate the valve clockwise tightly. If this doesn't fix the problem, there might be a slow leak. You can check it by spraying some soapy water and if it starts bubbling ...
How to Install the Replacement Rudder Control Arm for Pedal Pro Fish - 3.2m Preparation: Place the kayak on a stable surface, ensuring it won't tip over during the installation. Position it in a way that allows easy access to the rudder system. ...