L-Bracket and drilling for rackmount

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Hello,

I'm new to Protocase Designer, and I'm trying to build rack-mount ears, for 1U L-shaped rails (first picture).

As you can see on the second picture, the face I'm trying to drill has a huge red zone. Does that mean that I should not drill there?

If yes, what I am doing wrong? What would you advise me to do in order to build a similar ear design, but with drills in the center of the face?

Thank you for your help.