Mirror flange error

[Freddy]

Hi, I'm encountering a mirror problem. I tried to mirror the flange(in red color) with respect to "Front Plane"

But it is unsuccessful after I select the mirroring edge, is there any particular step I miss to make flange mirroring correctly?

[Mahesh_Sharma]

Freddy,

 Creo has limitaions on mirror of flange. It will allow mirrong of flange wall created with only one edge, if it is created using adjecent edges (as in your part), it will fail on mirroring.