Rigging Selection and Configuration
The Load Has to Travel Through the Sling
Selection begins with tension, not with a catalog picture. For a symmetrical two-leg bridle, tension per leg equals load ÷ (2 × sin θ), where θ is the angle between the sling leg and horizontal. A four-leg sling is normally assumed to share load between two legs only unless the load is rigid enough to guarantee otherwise - a classic exam trap. Hitch type modifies capacity: vertical is the baseline, choker reduces it (commonly 80% for wire rope and chain), and basket roughly doubles it when the legs are vertical and the load cannot roll out.
Match hardware so nothing becomes the weak link: shackle and hook working load limits at or above the sling's, safety latches present and functional, pins sized to the load rather than the shackle body, and eyebolts loaded only in the direction they were designed for. Protect what the hardware cannot resist - sharp corners, bend radius (the D/d ratio for wire rope), heat, and chemicals.
Traps include applying the angle factor to the vertical height instead of the sling length, using a choked sling as if it were vertical, and assuming the capacity on a tag applies to an untested configuration.
Rule of thumb: below 30° from horizontal, tension climbs steeply - at 30°, each leg carries the entire load, double its vertical share. Spread the pick points or use a spreader beam instead of accepting a flat sling.