Pee Pee. Are you really that daft?
Let me put it in simpler terms for you.
On the day that little yellow school bus that you were driven to that special school was build; when it was nice and new and exactly as designed, you could measure between various points throughout that bus (any point that was attached to the structure, super-structure or sub-structure), and record those measurements in a little note book (you probably colored in yours).
Then, after you drove that bus around - over a really bad road for instance - you could measure between those same points again. Then, you notice that several of the measurements differ from those recorded when it was new (in the regular school we called this geometry, trig, etc)
In aeronautical terms those changes in the measurements would lead us to believe that the structure had suffered some level of "Deformation" and those marks assist in measuring that deformation.
Next,
The "+" are alignment markers used by lasers during the etching/printing phase of the panel designs.
Why aren't they on all the panels?