The main aim of this work was to determine the safe weight of block that block moulders should lift and compare it with the weight that was actually lifted. The software of the model for Safe Weight of Lift (SWL) in the literature was employed in the study. The Load Strain Susceptibility Index (LSSI) was introduced and determined. The necessary anthropometric data of the twenty-selected block moulders and the task parameters were measured. The average weights (17.9; 22.79 kg for 6 inches and 9 inches block respectively) of blocks that the block moulders carried were more than the hazardous weight (13.91kg) of the blocks for the workers. The mean LSSI for safe, tolerable and hazardous were 1.0 (±0.00), 2.48 (± 0.26) and 3.94 (±0.52) respectively. It was concluded that the block moulders lifted more that the recommended safe weight which may lead to strain in the muscles of the workers.