The tested load at which a securing device (rope, chain, wire) will fail — the certification-basis for MSL calculation.
Regulatory detail & full definition
Breaking Load is the tested load at which a securing device (chain, wire rope, synthetic rope, web lashing) will fail. Manufacturer certification per ISO/EN test standards. Chief Officer uses BL as the certification input to derive MSL (maximum securing load) at the safety factor prescribed by the CSS Code (e.g. 50% for chain, 33% for synthetic).