{TAIL ~ A matrix} of apertures in {HEAD ~ the front wall} are selectively openable and closeable by a controller in response to the orientation of the eraser 
{ TAIL ~ A matrix } of apertures in { HEAD ~ the front wall } are selectively openable and closeable by a controller in response to the orientation of the eraser
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH