This zigag pattern of similar right triangles is formed by constructing a perpendicular to one line, intersecting with the other line and then constructing a perpendicular at the intersection point, and then continuing in the same way.
In the figure are many similar right triangles. One can also see dilations, and dilations composed with line reflection in the angle bisector. The scaling ratio between successive zigzags depends on the angle between the lines.
In the figure, you can drag a point or click the animation button to move the first point in the pattern back and forth.