Truck-mountable cargo rack

A truck rack, including rack components and rack accessories, to support cargo over a bed of a truck, and methods of constructing, assembling, mounting, adjusting, and using the truck rack. An illustrative truck rack comprises a tower and a base. The tower may have a foot and an upper end portion. The upper end portion may be configured to support a crossbar. The base may be configured to mount the tower on an upper wall region of a truck bed. The base may include a deck on which to support the foot and at least one securing device to secure the foot on the deck. In some examples, the at least one securing device may include a clamp configured to engage opposite edge regions of the foot. In some examples, the clamp may be configured to urge the opposite edge regions downward toward the deck.