This tip comes via InDesign Magazine’s tip of the day.

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Did you just draw a rectangle and end up with a stroke on it that you didn’t want? You can quickly change the fill and stroke attributes of any selected frame by pressing the following keys: Press the X key to toggle between the Stroke and Fill attributes. Press Shift-X and the fill color and stroke color will swap places. The comma key (,) applies the default color to the fill/stroke; the period key (.) applies the default gradient to the fill/ stroke; and the forward slash key (/) sets the current fill/stroke to None. These shortcuts work in Illustrator, as well.