What does the term "rectangular" signify in postal definitions?

The term "rectangular" in postal definitions relates to a shape requirement for mailing. When determining whether a package or piece of mail is acceptable for standard mailing classifications, the shape is crucial. Rectangular items typically meet the requirements for various mailing options offered by postal services, such as letter or flat rates. Non-rectangular items may not fit into standard sorting processes or could incur additional handling fees.

Understanding this classification helps to ensure that the item meets postal service guidelines for processing, which benefits both the sender and the postal service. Items that do not conform to this rectangular shape could face restrictions or additional costs due to their non-standard shape, which is why recognizing the importance of shapes like "rectangular" is vital for effective mailing practices.