Have you noticed this little gem yet?
Basically:
- Select a Fascia – the tool is revealed
- Click Modify Mitering
- Choose the option you want
- Click a fascia edge
Various options are available:
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Vertical miter
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Horizontal miter
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Perpendicular miter
You can learn more at:
Changing Mitering Options for Roof Fascia – WikiHelp
Its in 2012 too