Field help (SIHITMREF) 

It is the product reference for which a document line is recorded. Specifying it is mandatory.

It is possible to:

The entry of the product is used to initialize the Description and Sales unit fields, which can be modified. The sales unit can be modified on the condition that it is chosen from the suggested list that contains the sales and packing units from the product and product-customer records.

A warning message can appear to inform the user of the replacement of the entered product by the substitute product. This automatic substitution takes place if certain conditions are met:

SEEWARNING Once the line is entered, it will no longer be possible to modify the product code. It is necessary to delete the line and recreate it to modify the code.