Forged - Quenched and Tempered. Proper design, careful forging, and precision controlled quench and tempering gives maximum strength without excessive weight and bulk. Every Crosby Swivel hoist hook has a pre-drilled cam which can be equipped with a latch. Simply purchase the latch assemblies listed and snown on pages 89-91. Even years after purchase of the original hook, latch assemblies can be added. Load rating codes stamped on each hook. 322 Swivel Hooks use the same load rating code as 319 Shank Hooks, see page 84 for proper Hook Identification Codes. Hoist hooks incorporate markings forged into the product which address two QUICK-CHECK features: Deformation Indicators -- Two strategically placed marks, one just below the shank or eye and the other on the hook tip, which allows for a QUIC-CHECK measurement to determine if the throat opening has changed, thus indicating abuse or overload. Angle Indicators - Indicates the maximum included angle which is allowed between two (2) sling legs in the hook. These indicators also provide the opportunity to approximate other included angles between two sling legs. Note Carbon swivel hooks.75tC-15tC: proofload is 2 times working load limit.Designed with a 5 to 1 safety factor. Alloy swivel hooks 1.5tA-22tA : proofload is 2.5 times working load limit. Designed with a 4 to Isafety factor. Alloy swivel hook 31.5tA: proofload is 2 times working load limit. Designed with a 4 to 1 safety factor.