The propped block has {HEAD ~ several spaced horizontal propped surfaces} on {TAIL ~ the bottom} thereof which are formed at different heights with slopes formed in between 
on
The propped block has { HEAD ~ several spaced horizontal propped surfaces } on { TAIL ~ the bottom } thereof which are formed at different heights with slopes formed in between
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH