Select the line, under the Edit menu click on Arrange and then "Bring forward". This is assuming that you only have two objects. Should there be more than two then each object will have a level and the selected object will only move up one level with every "Bring forward" so several "Bring forwards" may be needed to get the object to the top. The "Bring To Front" option will move the item to the top without regard to its level relative to the other objects. The "Send backward" and "Send To Back" do the same thing only in the other direction.