A clamp to secure a tonneau cover to a frame of a cargo box includes a first clamp member coupled that has a first clamping surface. A second clamp member that has a second clamping surface. A ramp mechanism that causes lateral translation of the second clamping surface toward the first clamping surface, as the clamp moves between clamped and unclamped positions. A cam lock member positioned to engage with the second clamp member and includes a lever for placing the cam lock member in locked or unlocked states. When the cam lock member moves from the unlocked state to the locked state, the second clamp member moves toward the tonneau cover to the clamped position. When the cam lock member moves from the locked state to the unlocked state, the second clamp member moves away from the tonneau cover to the unclamped position.