Basic Question on Handler using pub.soap.handler:handlerSpec

I am working through the 10-1 Web Services Developer Guide trying to create a handler service. The guide states:
“However, handler services must use
a specific service signature. Integration Server defines the service handler signature
in the pub.soap.handler:handlerSpec specification”

I’m a Webmethods novice and the developer guide assumes I know how to do that. I am having a lot of trouble on figuring out how to create a service that specifies that signature and cannot seem to find any documentation on how do that simple task. Can anyone either direct me to documentation that explicitly addresses the signatures of services or step me through it?

UPDATE[u] : I figured out how to assign the specification but am trying to understand how to work with the input. I am actually trying to build a handler to deal with a custom header specified in a WSDL that my web service provider is created from. Can anyone direct me to samples that show custom header handlers?

Thanks