What it means is the lower tray (not the tray cover) has some plastic rails below it. The locking mecanism is a white nob/pin thats sticks up into the lower tray(u could say the nob/pin runs like a train on the rails/tracks).
The white nob/pin is the thing u push right with your swapkey to open the tray(and left to close the tray).
Sometimes the nob/pin jumps off the rail and the tray gets stuck.
So what u do is remove the 2 small screws at the lower left. Lift off the lower lid. push the nob/pin all the way to the right (laser and motor goes down). Place the lower lid back on in "open" position. insert one of the screws again( or both). Turn power on, and it should close automaticly. If not try again.
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