Blue cog

A Blue is used in the Clocktower quest to repair the blue wheel. It can be obtained by entering walking inside the rat cage. You can enter the cage by going north-east of the Clocktower, and south of the Camel Cage of the Ardougne zoo, and entering the trapdoor. Follow the pad and go through the wall. Do not try to grab it, since the dungeon rat will bite you.