A coupling structure for coupling first and second shell halves (200, 300) juxtaposed to each other, characterized by: first and second hooks (51, 52) mounted to the first shell half and a two-way securing hook mounted to the second shell half, wherein the first shell half has a first side and wherein said first hook includes a first resilient section extending from the first side towards the second shell half and a first clamping section extending laterally from said first resilient section along a first direction; said second hook including a second resilient section extending from the first side of the first shell half towards the second shell half and a second clamping section extending laterally from said second resilient section along a second direction opposite to said first direction, wherein said first and second hooks (51, 52) and the first shell half cooperatively define a clamping space thereamong; the second shell half having a first side, said two-way securing hook including a securing section projecting from the first side of the second shell half towards the first shell half, a first interfering section extending laterally from said securing section along said second direction and a second interfering section extending laterally from said securing section along said first direction: and said first clamping section having an inner inclined face proximate to said first shell half and an outer inclined face distal to said first shell half, said second clamping section having an inner inclined face proximate to said first shell half and an outer inclined face distal to said first shell half; wherein, when an external force is applied onto the second shell half in a first applied direction so as to move toward the first shell half, said first and second interfering sections (532, 533) respectively abut against said first and second clamping sections (512, 522) so as to cause said first and second hooks (51, 52) bend outwardly and laterally away from each other, thereby temporarily enlarging said clamping space to permit extension of said first and second interfering sections (532, 533) into said clamping space; wherein, when another external force is applied onto the second shell half in a second applied direction opposite to said first applied second direction, said first and second interfering sections (532, 533) respectively abut against said first and second clamping sections ( 512, 522) so as to cause said first and second hooks (51, 52) bend outwardly and laterally away from each other, thereby temporarily enlarging said clamping space to permit extension of said first and second interfering sections (532, 533) from said clamping space to an exterior of said clamping space. first and second hooks (51, 52) mounted to the first shell half and a two-way securing hook mounted to the second shell half, wherein the first shell half has a first side and wherein said first hook includes a first resilient section extending from the first side towards the second shell half and a first clamping section extending laterally from said first resilient section along a first direction; said second hook including a second resilient section extending from the first side of the first shell half towards the second shell half and a second clamping section extending laterally from said second resilient section along a second direction opposite to said first direction, wherein said first and second hooks (51, 52) and the first shell half cooperatively define a clamping space thereamong; the second shell half having a first side, said two-way securing hook including a securing section projecting from the first side of the second shell half towards the first shell half, a first interfering section extending laterally from said securing section along said second direction and a second interfering section extending laterally from said securing section along said first direction: and said first clamping section having an inner inclined face proximate to said first shell half and an outer inclined face distal to said first shell half, said second clamping section having an inner inclined face proximate to said first shell half and an outer inclined face distal to said first shell half; wherein, when an external force is applied onto the second shell half in a first applied direction so as to move toward the first shell half, said first and second interfering sections (532, 533) respectively abut against said first and second clamping sections (512, 522) so as to cause said first and second hooks (51, 52) bend outwardly and laterally away from each other, thereby temporarily enlarging said clamping space to permit extension of said first and second interfering sections (532, 533) into said clamping space; wherein, when another external force is applied onto the second shell half in a second applied direction opposite to said first applied second direction, said first and second interfering sections (532, 533) respectively abut against said first and second clamping sections ( 512, 522) so as to cause said first and second hooks (51, 52) bend outwardly and laterally away from each other, thereby temporarily enlarging said clamping space to permit extension of said first and second interfering sections (532, 533) from said clamping space to an exterior of said clamping space.