Field help (MANHLDREL) 

Click on the lock to place an order on hold.
Enter the hold code or select it by right click/selection.

The hold codes list depends on the miscellaneous table 204 and the access codes associated with the user.
The user who created the hold can always unlock the hold even if they do not have security for the access code for the hold.
If the hold code does not have an associated access code, there is no restriction on who can release the hold: any user with rights on the entry transaction in progress (the Hold Code field must be active) and whose "Authorization release control" (Chapter Sales, Group clearances, SCDTUNL parameter) is set to 'Yes' can unlock the order.

When an order if placed on hold, activity cannot be processed against this order until the order is released from hold. Delivery, invoices or preparation which systematically blocked. The hold of the allocation depends on the hold code.