This tray 15 comprises {HEAD ~ a well} 45 for holding {TAIL ~ markers} and the like, and upstanding therefrom a pair of spaced apart flanges 46 and 47 dimensioned for entry into the channel 41 of the extrusion 37 
for holding
This tray 15 comprises { HEAD ~ a well } 45 for holding { TAIL ~ markers } and the like , and upstanding therefrom a pair of spaced apart flanges 46 and 47 dimensioned for entry into the channel 41 of the extrusion 37
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH