The position of the tray is then secured with {HEAD ~ a fastener} screwably extending through the second arm into {TAIL ~ a friction fit relationship} with the shelf 
screwably extending into
The position of the tray is then secured with { HEAD ~ a fastener } screwably extending through the second arm into { TAIL ~ a friction fit relationship } with the shelf
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH