Through holes are formed when the beam penetrates through {TAIL ~ the entire thickness t} of {HEAD ~ the substrate} 18 
Through holes are formed when the beam penetrates through { TAIL ~ the entire thickness t } of { HEAD ~ the substrate } 18
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH