Sure thing.

Make a horizontal (or vertical selection) the size you want:

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Then use the rotate tool and make sure you select the "rotate selection" option:

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Click on the selection, and drag the little center point symbol to where you want to rotate around (or leave it at the default center), then click and drag the selection to the angle you want. Holding the ctrl key while draging will snap it to 15 degree increments:

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TO actually make it rotate the selection, click the "Rotate" button of the dialog that popped up, or just hit enter.

You can also use the move tool with the selection to place it more accurately:
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Then just fill with the desired colour:
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Hope that was clear enough!

-Rob A>