A mast assembly for a forklift truck includes a plurality of guide units. At least one of the guide units includes a sliding pad member made of a plastic material and having a block-shaped body, which is hollow, is open at its base side, and has a rectangular ring-shaped cross section. The sliding pad member has a rectangular, plain, front wall provided at the side of the block-shaped body opposite to the base side thereof. The front wall has a sliding contact surface. Reinforcement ribs are formed on the inner surface of the front wall. Grooves are formed in the sliding contact surface, extending along the respective ones of the reinforcement ribs and helping avoid formation of shrinkage depressions in the sliding contact surface. The block-shaped body includes first and second pairs of opposing side walls. Tabs are formed on the first pair of opposing side walls.