  We show that a Reissner-Nordstr\"{o}m (RN) black hole can be formed by
dropping a charged thin dust shell onto a RN naked singularity. This is in
contrast to the fact that a RN naked singularity is prohibited from forming by
dropping a charged thin dust shell onto a RN black hole. This implies the
strong tendency of the RN singularity to be covered by a horizon in favour of
cosmic censorship. We show that an extreme RN black hole can also be formed
from a RN naked singularity by the same process in a finite advanced time. We
also discuss the evolution of the charged thin dust shells and the causal
structure of the resultant spacetimes.
