In general, it is not recommended to adjust the dimensions of H - beams during on - site construction. H - beams are pre - fabricated in factories with precise manufacturing processes to meet the design requirements. Making on - site adjustments can compromise the structural integrity and quality of the beams. However, in some rare cases, minor modifications may be necessary. For example, if there are small errors in the alignment of connection points or if the H - beam needs to be slightly trimmed to fit into an existing structure during renovation projects. But these adjustments should be carried out with extreme caution and under the supervision of professional engineers. Specialized tools and techniques are required to ensure that the modified H - beam still meets the necessary load - bearing and safety standards. In most cases, any significant changes to the dimensions should be planned and made during the manufacturing stage in the factory to guarantee the quality and performance of the H - beams.