Teak logs are obtained through the Woodcutting skill by cutting teak trees. Chopping a teak tree requires level 35 Woodcutting and gives 85 experience. While teak logs are free-to-play items, the trees can only be accessed and cut by members.
While chopping teak trees there is approximately a 2.5% chance of receiving a special teak log. Special teak logs can be sold to the sawmill for 1,300 coins each, or used to convert all teak logs in your inventory into teak planks for free. Teak logs can also be turned into teak planks by paying the sawmill operators in Taverley, Varrock, or Prifddinas.