The line of Reflection must be equidistant from the figure and its refection and the line of reflection forms on 90 degree angle with any segment image with its angle. The pre-image ABDECF is reflected over the y-axis to make the image A'B'D'E'C'F'. The image's points are the same length form the point its reflecting you could use that too figure out all reflections if you knew the line of reflection. The way you find the line of refection with out a grid you have to use a compass and draw two angles between the twp points where the arches intersect draw your line of refection. Too right out a reflection you right it as r _{y-axis}.