Final answer:
Receiving backdoors should only be unlocked and open during the delivery or pickup of shipments to maintain security and prevent unauthorized access.
Step-by-step explanation:
The only time the receiving backdoors should be unlocked and open is when shipments are being delivered or picked up. This is a security protocol that helps to prevent theft and ensure the safety of the warehouse employees. The backdoors should remain locked at all other times to restrict unauthorized access and maintain the integrity of merchandise within the facility.