The UII data can be 'constructed' in one of many formats; the most common formats are UII Construct #1 and UII Construct #2. The key to determining whether to use UII layout Construct 1 or Construct 2 layout lies in how a company serializes item numbers. Based on the current enterprise configurations: If items are serialized within the enterprise, use Construct #1. If items are serialized within the part, lot, or batch number, use Construct #2.