Edit Bar control: Ok
This tool adds a parallel constraint to two or more entities that have a direction, such as lines and text entities.
To use the tool, identify two suitable entities. You can also hold the Shift key down whilst identifying them to include more entities. When you have finished identifying them the entities will be constrained so that they are parallel to each other.
After creating the parallel constraint you can hover your cursor over the constraint and all related entities will be highlighted.
Shift Modifier
You can also hold the Shift key down whilst identifying them to include more lines. When you have finished identifying them, all lines will be included in the constraint.
After identifying two lines whilst using the Shift modifier the Ok button becomes active on the edit bar: 
You can now click this button to finish the tool and apply the constraint.
Pre-selected Entities
Alternatively, you can select two or more lines and then start the tool. The parallel constraint will then be added to all selected lines.
NOTE: Whilst this tool can be used to move entities so as to satisfy the constraint, it is recommended that entities are created in the desired position.