{HEAD ~ Apparatus} and methods for controlling {TAIL ~ application} of a substance to a substrate involve the use of a functional agent that blocks the substance from or attracts the principal substance to the substrate 
{ HEAD ~ Apparatus } and methods for controlling { TAIL ~ application } of a substance to a substrate involve the use of a functional agent that blocks the substance from or attracts the principal substance to the substrate
HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH