BS 2090 – Specification for hook spanners, peg spanners, coupling wrenches and the related slots, holes and horns
Dimensions, materials of hook spanners (C-spanners) and peg spanners; dimensions of slots and holes in circular and similar nuts in which spanners engage. Dimensions, materials of coupling wrenches for hoses up to 100 lb/sq in (not including fire hose couplings). Main nominal dimensions of circular and rectangular horns included.