Requirements that all US bound air cargo is examined at a piece level means that each individual box or item in a shipment must be examined in person or by a machine before being packed and ready for shipping.
Examination might be in person or by approved equipment (ie x-ray or explosive detection) before being packed onto pallets etc for shipping.
Cargo can be examined prior to delivery to the airport by an Enhanced Air Cargo Examination (EACE) provider.
Alternatively organisations can register as a Known Consignor, a new category of industry participant under the new arrangements. Through strict security procedures and business processes a Known Consignor will be able to secure their shipment at the source without requiring further examination prior to being loaded onto the aircraft.