What are projection, dimension and leader lines?
A drawing needs to give the person making the component all the information they need. Dimensions and notes are written on the drawing. Lines are used to explain how these dimensions and notes relate to the object. This is called ‘dimensioning a drawing’. Projection lines are thin continuous lines that come away from the drawing at the feature being sized. Dimension lines are thin continuous lines with an arrowhead on both ends. The dimensions are placed on top of the dimension line. Dimension lines should not be placed over the outline of the drawing unless there is no other option. Leader lines are thin continuous lines that indicate where dimensions, notes and item numbers apply. The leader line should terminate with an arrowhead at the feature end and a short horizontal line (approx 5 mm) at the dimension end.
