The rates of wages to be paid shall be posted
by the contractor in a prominent and easily accessible place
at the job site, and a copy of the rates of wages required to
be posted shall be given to each laborer and mechanic employed
under the contract by the contractor at the time each laborer
and mechanic is employed, except that where there is a collective
bargaining agreement the contractor does not have to provide
the contractor's employees the wage rate schedules.