The pound‑inch (lb·in) is a standard unit of torque that quantifies the rotational force produced when a one‑pound force is applied at a distance of one inch from a pivot point, and it is commonly symbolized as lb·in or lb‑in; engineers and technicians use this measurement to specify tightening specifications for bolts, fasteners, and machinery components, making it essential for ensuring proper assembly, preventing equipment failure, and achieving precise performance in automotive, aerospace, and industrial applications where accurate torque control is critical.