California Code, Public Contract Code - PCC § 21007

Before the execution of such contract, a bond shall be executed and filed, running to the county, in an amount not less than one-half of the contract price of the work, signed by the contractor and two or more sureties, who, unless surety companies, shall qualify before an officer entitled to administer the oath, in a sum aggregately equal to the amount of the bond, each surety in the amount for which he or she becomes surety.  Such bond shall be conditioned for the faithful execution of the contract by the contractor, and for the payment by him or her for all labor and materials furnished for or in the doing of the work.  The form and sufficiency of said bond shall be passed upon by some member of the board of supervisors, and such bond shall inure as well to the benefit of any and all persons furnishing labor or materials for the work as to that of the county.