The item that may be reserved for customers typically includes those that are pre-packaged or wrapped, such as wrapped crackers on a plate. These items are considered safe to be reserved or even re-served to customers since they are individually packaged and protected from contamination.

If the question is about what items a business allows customers to reserve for purchase, this often depends on the store's policy but frequently involves pre-packaged goods or personalized/customized products that customers request in advance to ensure availability.

In summary:

• Pre-packaged items like wrapped crackers can be reserved or re-served safely.
• Customized or personalized products can also be reserved for customers on request.
• Policy on reserving items may vary depending on the business context.

This addresses the notion of which items may be reserved or re-served to customers in terms of food safety and retail reservations.