Man uses his right hand more often than his left, and consequently his various instruments and equipment (staircases, locks, watch springs, etc.) are designed to be used in a right-to-left manner.
L'homme se sert plus souvent de sa main droite que de sa main gauche, et, conséquemment, ses instruments et ses appareils, escaliers, serrures, ressorts de montres, etc., sont combinés de manière a être employés de droite à gauche.