tunnel protectors
Polarisman_98 mentions about the screws that go through the tunnel protectors to hold them in place, you do not drill any holes through the extrusions that the protectors slide onto, the screws, from what I understand, are to keep the protectors from being driven forward if the track were ever to touch them. As you will notice from the second picture, the screw is actually to the rear of the extrusion.
Those screws(which are horizontal through the protector) only need to be tightened a small amount.
Should look like this when all done: