The photos of the disks should be a reminder to everyone that they should be removed before a garage has to take them off for some reason.

If the caps are not aligned with their indexing tabs locating into the indexing point on the wheel severe damage will be caused by the mechanic banging them on, he may have a few goes at this before realizing that he has to align them first.
To put the caps on first locate them in the indexed position with the indexes mated correctly and holding them firmly at that indexed position and at the resulting angle tap them on the opposite side using the side of a fist.