Abstract: A conveyor is arranged to pass lumber strips through a tank of treating liquid and includes pairs of upper and lower flexible lines arranged to receive lumber pieces therebetween. Hold-down apparatus is engageable with the upper flexible lines and is arranged to force such upper lines toward their lower lines to frictionally hold lumber pieces between the upper and lower lines and also to force the assembly of upper and lower flexible lines and lumber pieces down below the liquid level in the treating tank for coating the lumber pieces during the pass of the conveyor through the tank. In a preferred arrangement, the flexible lines comprise resilient type ropes wherein the conveyor assembly is forced down below the liquid level by a stretching of the ropes. The hold-down apparatus is pivotally supported adjacent one end of the tank and has longitudinally spaced pulleys for guiding the ropes, these pulleys being arranged to vary the submerged length of travel by pivotal adjustment of the hold-down apparatus.