{HEAD ~ The stair tread mechanism} is connected with a window lock and initial movement of the stairs unlocks {TAIL ~ the window} 
{ HEAD ~ The stair tread mechanism } is connected with a window lock and initial movement of the stairs unlocks { TAIL ~ the window }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL