The graphic indicates the path of a message and a point at which the message is intercepted and processed.

In the graphic, an arrow leads from a system labeled Sender to an envelope that has a Header part in it besides other parts. This envelope is labeled SOAP Message. An arrow leads from this envelope to a block labeled Message Handler. This block contains a pair of wheels in its top-left corner. An arrow leads from this Message Handler block to another system that is labeled Receiver.