SAP Sales and Distribution
Observations related to rejection key includes
Understanding Rejection keys
Reason for Rejection is a indicator available at sales document item level for the purpose of identifying the rejected items. This is more or less equivalent to deletion indicator set in a purchasing document but a fixed reason for rejection can be assignment which can be used for reporting purposes. In addition there are few process behaviors that can be controlled using configuration.
Refer to following documentation for details.
Reason for Rejection in Sales documents
SAP Note : 1771533 - Rejected line item shown in VF04