Gives advice on three levels of imperfections in a manner that permits application to a wide range of welded fabrications. The levels do not refer to the fitness for purpose of the product; the levels refer to production quality. Applies to: all welding positions; manual, mechanised and automatic pressures; some welding processes and their defined sub processes; unalloyed and alloyed steels; butt welds, fillet welds and branch connections; materials in the 3mm to 63mm thickness range. Does not cover metallurgical aspects.