SOAP Client header

Hello,

Can someone tell how to create a header within a SOAP Message for sending
wwith HTTP Client? And how to use x509 certificate with this HTTP Request?

<SOAP-ENV:Envelope>
<SOAP-ENV:Header>
<kai:identificatie>
<username>
</username
</kai:identificatie>
</SOAP-ENV:Header>
<SOAP-ENV:Body>
XML
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>


Thanks for the help.
Regards,
Wilco