HH: Ring-type structure, that is, there are hanging rings at both ends.

HG: Ring rod structure, that is, the upper end is a lifting ring and the lower end is a connecting rod.

GG: Rod type structure, that is, the two ends are connecting rods.

GH: Rod ring structure, that is, the upper end is a connecting rod and the lower end is a lifting ring.

GH and HH structures are the most commonly used.

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