Abstract: A fork lift truck includes a mast support bar to which the mast supporting carriage and fork lift tines are mounted. The mast support bar includes a central arc-shape segment on which a concentric arc-shape mast support sleeve is slidably mounted. The mast is mounted to the sleeve and power means are provided to slide the sleeve in either direction on the mast support bar. When the fork lift truck encounters uneven ground so that the wheels on one side of the truck are higher than the wheels on the other, the operator will slide the mast support sleeve with respect to the mast support bar to keep the mast in a vertical position over the truck.