Self-adaptive systems autonomously change their behavior to compensate for faults or to improve their performance. Evolvable hardware, which combines evolutionary algorithms with reconfigurable hardware, is often proposed as the cornerstone for systems that use self-adaption for fault recovery. Although evolvable hardware was first introduced over 15 years ago, there are few, if any, fault tolerant self-adaptive systems in operation today. One primary reason why these unfortunate circumstances have arisen is many designers—and not limited to just designers from the computational intelligence community—do not really understand how to build a basic fault tolerant system, let alone a self-adaptive fault tolerant system. This chapter describes how fault tolerant systems are built. A model for designing fault tolerant systems that rely on evolvable hardware for fault recovery is presented.