Glossary

Working Load Limit (WLL) is the maximum load that a lifting or rigging component is permitted to carry in normal service when it is used correctly and within its rated configuration. It is a rated, allowable load that already includes a margin of safety relative to the component’s minimum breaking strength, so it is not the load at which the item fails.

WLL is set by the manufacturer and is tied to specific conditions of use, such as the component size and grade, thread engagement, temperature limits, and the type of connection (e.g., straight lift vs. angled/sling loading). For many rigging products, the WLL is derived from the minimum breaking load divided by a design factor (often 4:1, 5:1, or higher depending on the product category and standard), and it may be reduced for non-ideal loading conditions like side loading, shock loading, or elevated temperature.

In industrial fastener contexts, you’ll see WLL on eyebolts, hoist rings, lifting lugs, lifting sockets/inserts, shackles, turnbuckles, and other rigging hardware. The WLL is the number you use for safe selection and planning; exceeding it can cause permanent deformation, loss of preload/fit, fatigue damage, or catastrophic failure—even if the component does not break immediately.