Capping, or the surgical implantation of a mechanical Cap that is connected with a human subject’s brain, is a key method the Tripods use to exercise control over humanity. As such, Capping becomes a symbol of the methods by which totalitarian governments or other powerful organizations seek to control the very thoughts of their subjects. Capping generally takes place when an individual reaches about 14 years of age, which, in medieval times, marks the beginning of young adulthood; it is also the time at which the risk of rebellion against the Tripods would begin to rise.

Those who are successfully Capped come to view the Tripods as benevolent beings worthy of veneration, even in cases where the Tripods openly exploit those same individuals, as was the case for Eloise. Capping thus relates to Christopher’s exploration of Freedom Versus Security, with the procedure offering a certain stability to those who undergo it at the price of a loss of individuality, creativity, and critical thinking. Capping can be seen as a symbol of virtually all the techniques a dominant hegemonic force may use to ensure its continued domination, including subtle techniques to shape people’s very perceptions.