A slide bar passes through the doorway and is pivoted at one end to {HEAD ~ a movable end} of {TAIL ~ the upper arm} , and at the other end to a fixed bracket on the other side of the doorway  
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A slide bar passes through the doorway and is pivoted at one end to { HEAD ~ a movable end } of { TAIL ~ the upper arm } , and at the other end to a fixed bracket on the other side of the doorway
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH