Weigh In/Out - The certification, by the clerk of scales, of a rider's weight before/after a race. A jockey weighs in fully dressed with all equipment except for his/her helmet, whip and (in many jurisdictions) flak jacket.
Weight-For-Age
A practice that allows horses of different age and sex to compete on equal terms. The weight a horse carries is allocated on a set scale according to its sex and age.