the cheapest way to train construction is to make CastleWar Armor / mithril, addamant, or rune Armor in the Skill Hall. Look at this: a 'Repair Bench' needs 2 Oak planks and gives 120xp for every items, oak planks gives 60xp ea except : Cw armour 1: 135xp Cw armour 2: 150xp Cw armour 3: 165xp Mithril armour: 135xp Adamant armour: 150xp Rune armour: 165xp