Beware of the Sucker Wing Ribs Flanges!

What is a Sucker Wing Rib Flange? It is explained in the following picture:

The arrow is pointing to the sucker. You can see that this part of the flange is recessed and carries just one hole: this is what makes it a sucker! What may happen when you push the rivet while riveting the skins of the bottom of the wing (W 1201 L/R) is that the tiny flange which offers little resistance will be pushed and the rivet's shop head will set under it. It happened to me in two places including this one and I was unfortunately too busy correcting this mistake to take a photo before reworking it.
It's only because we were two looking inside the wing after flipping it that we noticed. I'm afraid that it may happen to others who might not notice, hence my warning!