What is the purpose of these labels on an aircraft's wings? During a flight on an Airbus neo I was looking at the wing on my left, and noticed a set of labels on it. A few can be seen in the below image:  



(The third one on the right is not readable, I was focusing on capturing something else.)

After a bit of working on it I think I found part of the pattern, with letters starting from A in the front of the engine and going B, C, D, etc. while moving farther from the front, and R, L and T standing for Right, Left and Top.

Now, while building a Lego plane set it could absolutely make sense, or maybe if you buy a plane from IKEA... But why on a real life aircraft? Just for something like visual inspection after build?
Closer than you may think: notice that these panels all have fasteners visible-- these panels are removed frequently for engine work.  The labels are there so that the maintenance crews can both more easily reattach the panels, and so when they're inspected (again as part of maintenance) you're can quickly confirm that everything is in the right place.

When you have a plane in parts, all the panels start to look very similar lying on a workbench... Having the labels makes things more efficient and safer.