This chapter reports on the clock-proxy auction, a hybrid combinatorial auction design in which the process of auction begins with a clock phase and ends with a proxy round to promote efficiency. This format combines the advantages of both the designs as the efficiency of the proxy auction is complemented with the logical price discovery of the clock auction. A comparison between the clock-proxy auction and the simultaneous ascending auction that establishes the superiority of the former on the efficiency and revenues front is also made.