The attorney / plaintiff / creditor can request issuance of a civil bench warrant from the court under certain circumstances (e.g., failure to appear for a subpoena, violation of a court order, etc.). Service of a civil bench warrant will require a letter of instruction and required fees payable to the sheriff where service is to be made. The court issues a civil bench warrant (or civil warrant of body attachment) and forwards it, along with the letter of instruction and fees, directly to a sheriff for service.
Depending on the jurisdiction, some courts will send the warrant / documents / fees to the sheriff in their own county, who then forwards the information to the sheriff in the county where the service is to be made. The sheriff will not accept a civil bench warrant if it arrives from any source other than a California court or another California sheriff.