Thus, once an instrument initially is placed in the holder, each flap customizes itself to {HEAD ~ the shape} of {TAIL ~ each instrument} 
Thus , once an instrument initially is placed in the holder , each flap customizes itself to { HEAD ~ the shape } of { TAIL ~ each instrument }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL