The flexible sheets are attached to structural members, that is, to {TAIL ~ purlins} beneath {HEAD ~ the roof panels} 
The flexible sheets are attached to structural members , that is , to { TAIL ~ purlins } beneath { HEAD ~ the roof panels }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD