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