We now take the straightedge and draw a ray next to the line segment. We can call the end of the ray A.
We now take the compass and set it at the length of XY.
We now move the compass over to the ray. We place the pointed end at A and draw a line across the ray and by that marking a point on the ray.
We call the point we marked on the ray B. We mark it properly with a dot and do our best to erase the part of the ray we have which overshoots point B.
The segment AB has the same length as the segment XY.
