21. For as long as the apprentice has not completed the apprenticeship of a qualification element, the apprentice may carry on the work referred to in section 3 for the required certificate of qualification only under the supervision of a holder of such a certificate of qualification who is on the premises and near the apprentice.
After completing the apprenticeship of a qualification element and for as long as the certificate of qualification has not been issued, the apprentice may carry on that work only under the supervision of a holder of a certificate of qualification required for the supervised work.