HSN Code 4906 refers to "Plans and drawings for architectural, engineering, industrial, commercial, topographical or similar purposes, being originals drawn by hand; handwritten texts; photographic reproductions on sensitised paper and carbon copies of the foregoing." This classification code is essential for identifying various types of plans and drawings for import/export purposes based on their nature and intended use. Common products under HSN Code 4906 include architectural blueprints, engineering schematics, industrial designs, commercial layouts, and topographical maps. Additionally, the GST rate for these items under this code supports accurate trade compliance.