In this exercise, we sketch a rectangle and constrain the lower right corner of the first sketch to 0, 0, 0. Constraining a sketch to the origin makes the sketch behavior predictable and eliminates two degrees of freedom by defining the XY location.
To begin:
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Start a new mm part. Sketch a rectangle with the lower right-hand corner located at 0,0. 
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Start the Dimension command. - Create a horizontal dimension with a value of 160 mm and a vertical dimension with a value of 86 mm. The sketch is fully constrained. Note: If the sketch is not fully constrained, make sure that the sketch is constrained to the Origin.
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Exit the sketch. Use the Finish Sketch command, the 
Return command, or right-click and choose Finish Sketch from the marking menu to exit the sketch environment. -
Start the Extrude command. Extrude the sketch 15 mm.