Stencil rubber

[Jean Abou Samra]

Hi,

Is there a way to restrict the drawing of a stencil to certain parts?

For example, suppose that I want to join the letters A and B in a custom 
letter that is half an A in the left half and half a B in the right 
half. How can I do that in a markup?

I can add a white box to hide part of the A, getting half an A. I can do 
the same for B. But if I \combine the two, the white half of the B get 
printed over the A...

Any help would be highly appreciated.

Jean