Hook for clamping two covers

A hook for clamping a first and a second covers together, the hook comprising:

• a first hook element fixed on the first cover, the first hook element comprising:
• two supporting panels extending from a surface of the first cover and spaced from each other;
• and
• a first flat panel connecting tops of the two supporting panels, wherein a receiving space is formed between the first cover, the two supporting panels, and the first flat panel, and
• a second hook element fixed on the second cover, the second hook element comprising:
• a supporting member extending from a surface of the second cover;
• a second flat panel extended from a distal end of the supporting member and parallel to the surface of the second cover;
• and
• a groove formed between the supporting member and the second flat panel;
• wherein when clamping the first and the second covers together, the first flat panel of the first hook element is slid into and engaged with the groove of the second hook element, and clamped between the second flat panel and the supporting member of the second hook element.