The sheriff shall, during fair and reasonable weather, when the same can be done without extra expense to the county, procure employment for and set at work such persons convicted of violating NRS 207.030 who are serving out their term of imprisonment; and to this end, upon application of any road supervisor, superintendent, foreman or other overseer or custodian of any public works, buildings or grounds, the sheriff may deliver into the custody and charge of such person making the application such prisoners, to do labor as required, who after working hours of the day, or after suspension of labor from any cause, must be returned into the custody of the sheriff of the county for safekeeping until again required for labor.