roof rack(n = noun.artifact) luggage rack - carrier for holding luggage above the seats of a train or on top of a car;
is a kind of carrier

bicycle rack, bomb rack, coat rack, curb roof, dish rack, dress rack, french roof, gable roof, gambrel roof, hip roof, hit the roof, hurricane roof, luggage rack, magazine rack, mansard roof, music rack, pipe rack, plate rack, rack, rack and pinion, rack of lamb, rack railway, rack rent, rack up, raise the roof, roof, roof garden, roof mushroom, roof of the mouth, roof peak, roof rat, saddle roof, saddleback roof, ski rack, slate roof, spice rack, thatched roof, tie rack, tile roof, towel rack