Temporary dimensions snap to the nearest perpendicular element and adjust by a defined value.
You can define the snap increment. If you define the snap increment to 6 cm, the dimension increases or decreases in values of 6 cm as you move the element to place it.
After you place the element, Revit displays the temporary dimensions. When you place another element, the temporary dimensions for the previous element no longer display. To view the temporary dimensions of an element, click Modify and select the element. Remember, the temporary dimensions are to the nearest element, so the dimensions you see may be different from the original temporary dimensions. To display dimensions at all times, create permanent dimensions.
The size and background of temporary dimensions can be modified in the Options dialog under the Graphics tab. By adjusting these settings, the text dispalyed when using the measure tool will also be affected.
You can modify temporary dimensions to reference desired elements by moving the witness lines. You can also specify the display and placement of temporary dimensions.