To show edges in an assembly, make sure that you have the Shaded with Visible Edges command turned on. This command is found on the View tab in the Style group.

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You can also control the color of the edges using the Single-Color Edges command also found on the View tab in the Style group.

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You can select a standard or custom color to use for edges from the Select Edge Color list. Found on the Single-Color Edges command flyout menu.

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Note: Edge display can also be controlled by a Face Style.

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