How do you get a wooden plank in runescape

If you are a member, just buy or cut some normal logs, and go to the sawmill east of Varrock, and make a plank for 100 gp. If you are F2P, you can try keeping up an offer in the grand exchange for maximum price, or (faster) go to lvl 21 wilderness near clan wars and pick some planks up in the graveyard of shadows, as several planks respawn there.