Preferably, the invention relates to {HEAD ~ a device} wherein {TAIL ~ the device} comprises a guiding rail and an interconnecting bar 
wherein
Preferably , the invention relates to { HEAD ~ a device } wherein { TAIL ~ the device } comprises a guiding rail and an interconnecting bar
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH