To Apply an Equal Distance Constraint

Select the Equal Distance Constraint tool ( Drawing > Constraints > Dimensional ).
Select the first profile or profile segment.
Select the second profile or profile segment.
Select the third profile or profile segment.
(Optional) Press <Ctrl> to select more profiles or profile segments.
Note: All the selected profiles or profile segments must be parallel to each other.

The perpendicular distance between these three segments become equal.

Applying an equal distance constraint to segments of a profile