What is a dimension line?

Lines that define the parameters of a dimension.

Dimension lines are thin lines terminating in arrowheads. Place dimension lines no closer than 3/8" from the object outline. Parallel dimension lines should be a minimum of 1/4" apart. You may place parallel dimension lines more than 1/4" apart so long as the spacing between dimension lines is uniform throughout the drawing. Dimension lines are generally broken in the center of the line to provide a space for the dimension figure. Dimension figures for parallel dimension lines are staggered. In some structural or architectural drawings, you may find dimension figures placed above the dimension line.