How do I make by webControl NOT show up in the toolbox?

[chambersdon]

I have a DLL with several custom web controls in it. When I add this
dll to the toolbox all of the controls appear. The problem is that
some controls are used by other controls and should never be used
directly. How can I I make these controls not appear in the toolbox?

I tried removing the ToolBoxData attribute from the class declaration
but this did not help.

Thanks,
Don