Final answer:
Carriers sign a receipt such as PS Form 3849 for accountable items, which serves as a record of delivery or delivery attempt by the postal service.
Step-by-step explanation:
When carriers are handling accountable items, they are typically required to sign a receipt that verifies the acceptance and delivery of these items. Accountable mail includes registered, insured, certified mail, and other types of mail which require tracking and safe handling. The most common form used in the United States is PS Form 3849, also known as the Delivery Notice/Reminder/Receipt. This form is used by the United States Postal Service and is filled out by the carrier when accountable mail is delivered or a delivery attempt is made. It provides a record of delivery, ensuring that both the postal service and the sender can confirm the item's handling.