While shelf clouds can often signify the leading edge of gusty winds, they do not necessarily mean the winds are severe.  Therefore shelf clouds are not reported to the NWS.  However, if a shelf cloud is sighted, a storm spotter should be alert to the possibility of strong winds in the next few minutes.  Take shelter and wait for the winds to pass.  If the winds meet severe criteria (greater than 57 mph or produces damage), then he/she should call in a report to the NWS as soon as safely possible.