What is the purpose of the five-sided nuts on fire hydrants?

The five-sided nuts on fire hydrants serve primarily to deter vandals. This unique shape makes it more difficult for untrained individuals or vandals to access the internal workings of the hydrant. By using a specialized tool that is typically required to operate these nuts, fire departments can ensure that only authorized personnel can open and use the hydrants for firefighting purposes. This helps protect the hydrant from tampering or damage, which can be critical in emergency situations where immediate access to water is necessary for firefighting efforts.

The other options do not accurately reflect the primary function of the five-sided nuts. While they may have implications for functionality or safety, their primary design purpose is deterrent in nature.