Post a picture it could be many differant styles.
If there's a level mounted to the side of the tub to work it then remove the two screws and pull it out.
http://www.lowes.com/cd_how+to+repair+tub+drain_1306180716_
If there's a level mounted to the side of the tub to work it then remove the two screws and pull it out.
http://www.lowes.com/cd_how+to+repair+tub+drain_1306180716_