The thread lubricator is used for dry leather that flags (lifts the leather up when the needle starts to come out of the leather), nylon webbing, or any other synthetic materials. The thread lubricant helps keep the needle cool. You will have to fill the thread lubricator with the Silicone Thread Lubricant that we have available as well. The thread lubricator is magnetic, so you can attach it to the top of the machine and use as part of the threading . You will thread the lubricator before the first tension assembly.