WLL / SWL
Working Load Limit (a.k.a. Safe Working Load): the maximum load you may apply in service. WLL = MBS ÷ safety factor.
RiggingSense · Reference
The rigging words everyone uses and nobody defines.
WLL, MBS, D8+, uplift, skew, superposition. This is the glossary built into RiggingSense, published in full — twenty terms, in the language the trade actually speaks, with the units mess explained rather than glossed over.
This is a training reference, not a standard. RiggingSense teaches the statics behind stage rigging; it does not certify anything, and real work follows the current standards and a qualified rigger. Where a term names a regulation, look up the version in force where you are.
MBS
Minimum Breaking Strength: the load at which the hardware fails in testing. Never a working number.
Safety factor
The ratio between breaking strength and permitted load. Covers wear, dynamics, and the unknowable.
Point load
A load applied at one spot — a hung amp rack, a chain bridle apex on a beam.
UDL
Uniformly distributed load — spread evenly along a length, like deck, LED wall or a full rig of fixtures. kg/m.
Dead vs. live load
Dead load: the structure and everything permanently on it. Live load: what varies — performers, moving scenery, snow on a roof.
Reaction force
What a support pushes (or a hoist pulls) back with to keep the structure in equilibrium.
Bending moment
The internal "torque" that bends a beam — force × distance. What span ratings actually limit.
Span table
Manufacturer data: allowable load per span for a truss type. Derived from bending and deflection limits.
Bridle
Two (or more) legs sharing one load between anchor points, meeting at an apex. Leg tension depends on angle.
Basket / choker hitch
Ways of wrapping a sling: basket doubles capacity, choker reduces it. Hitch factors modify the WLL.
D8 / D8+ / C1
German hoist classes: D8 (SF ~4, no loads over people without secondary), D8+ (SF 10, static holding over people), C1 per DGUV V17 (moving loads over people). Look up the current standard for real work.
Uplift
A support reaction that goes negative — the structure wants to lift off. A chain hoist cannot push: uplift = slack chain = unstable.
Cantilever / overhang
Beam sticking out past its support. Loads there unload — and eventually uplift — the far support.
Skew
Heavily uneven load split between hoists. One approaches its WLL while the other runs light.
Dynamic loading
Short-lived force multiplication from movement — snubbed stops, bouncing lifts. Part of why safety factors exist.
Secondary safety
An independent second means of support (safety steel) that catches the load if the primary fails.
kg vs. kgf vs. kN vs. daN
kg is mass; hanging 1 kg exerts 1 kgf ≈ 9.81 N of force. Engineering documents use kN (1 kN ≈ 102 kg) or daN (1 daN ≈ 1.02 kgf). This tool displays kg because the trade does.
Superposition
For reactions, load cases can be solved separately and added — the basis for combining point loads with self-weight.
Centroid
The balance point of a distributed load — where its equivalent point load acts (midspan for a full-span UDL).
RiggingSense · Reference
Learn the statics, not just the vocabulary.
RiggingSense is free: drag loads in a live sandbox, watch reactions and bridle tensions solve step by step with your own numbers, and work through a trainer that explains every answer.
