1. Identify each item
Use one row for each size. Include a product name and standard reference, or a dimensioned drawing. A supplier should not have to infer the part from a general description such as "steel bolt".
2. Make dimensions unambiguous
State thread diameter and pitch, length and relevant tolerances. For bolts, say whether the length is measured under the head. For washers, include the inside and outside diameters and thickness.
3. Specify the material and finish
Give the required material, grade and coating. If you do not know them, explain the use and environment so the supplier can identify what needs clarification. Do not treat a colour or appearance as proof of a coating specification.
4. Add quantities and the destination
List pieces per item, packing requirements, destination and required timing. Ask for freight separately if you need a clear comparison of unit prices.
5. Check the response
Compare the quoted specification to your request. Resolve substitutions, documents, samples and packing before committing to the order.