ZCML File
meta.zcml

<configure
    xmlns:meta="http://namespaces.zope.org/meta"
    >
<meta:directives
    namespace="http://namespaces.zope.org/browser"
    >
<meta:directive
    name="viewlet"
    schema=".metadirectives.IViewletDirective"
    handler=".metaconfigure.viewletDirective"
    />
</meta:directives>
</configure>