To define {TAIL ~ a stable position} of the draft shield element on the sample changer, the seating rim of {HEAD ~ the draft shield element} sits in a matching seating recess of the sample changer 
To define { TAIL ~ a stable position } of the draft shield element on the sample changer , the seating rim of { HEAD ~ the draft shield element } sits in a matching seating recess of the sample changer
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH