The present utility model includes a casing body (100, 100b, 100c), recessed rotary hooks (300), a driver (700, 702, 703) and a latch body (800, 800b, 800c). One end of the envelope body (100, 100b, 100c) is provided with a front end opening (110, 110b, 110c). The embedding rotary hooks (300) are arranged in the casing body (100, 100b, 100c), and can pivot relative to the casing body (100, 100b, 100c), the embedding rotary hooks ( 300) include front end portions (310) and rear end portions (320), the front end portions (310) extend at least partially outside of the front end opening (110, 110b, 110c), the rear end portions (320) extend in the opposite direction from the front end portions (310). The driver (700, 702, 703) is arranged in the casing body (100, 100b, 100c), and can selectively move its position to change the opening width (W311 ', W311' ', W311' '') of the front end parts (310). The lock body (800, 800b, 800c) is arranged in the casing body (100, 100b, 100c), when the lock body (800, 800b, 800c) is closed, the lock body (800, 800b , 800c) limits the movement of the drive device (700, 702, 703). Fig. 1
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