There are many real world examples of similar figures. For example reading a map to determine the distance between two destinations, reading a blue print to determine the size of the building, and enlarging an image to name a few. You can more than likely think about other examples as well.
Draw a diagram for the following:
If you had a measuring tape and or a mirror, how could you find the height of a tree without climbing it? What would you need to know?
You are playing a game of tennis and are serving a ball, how do you use similar triangles to help you figure out how to get it just over the net and into the court?
Create your own example and draw a diagram.
These examples introduce indirect measurement and provide situations that will apply to the lesson.
You are reading a map or a blueprint, know the dimensions on the blueprint and want to find the real dimensions. Conversely you may know the real measure and want to find the dimension on the blueprint.