In this paper, we consider a similarity control problem for the plant and the specification modeled as nondeterministic automata. This problem requires us to synthesize a nondeterministic supervisor such that the supervised plant is simulated by the specification. We show that a state-controllable subautomaton of the synchronous composition of the observer automaton of the plant and the specification can be used as a solution to the similarity control problem. It is desirable that a supervisor be as permissive as possible. Thus, to synthesize a similarity enforcing supervisor, we construct the largest state-controllable subautomaton of the synchronous composition of the observer automaton of the plant and the specification.