The preheat module has {HEAD ~ a vertically moveable rack} and is loaded with various sized batches of {TAIL ~ wafers} with no vacant positions between them 
The preheat module has { HEAD ~ a vertically moveable rack } and is loaded with various sized batches of { TAIL ~ wafers } with no vacant positions between them
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH