Three places not to step on an airplane:
Wheel fairings (high wing or low wing): Want to hear an owner howl? Step on a wheel pant. Children are especially likely to do this, because it looks like a step made just for them.
Flap (low wing): Keep your feet off the flap. A helpful “no step” placard may be visible.
Any place where there’s no wing walk (low wing): The wing walk material gets worn down over time and needs replacement periodically.
You can have a lot of fun guessing—radar reflector? ice detector? Emergency emery board?—but the purpose of the strut step is to provide a place for you to brace your foot along the strut of a high-wing aircraft, so that you can climb up and see the top of the wing.
You want to be able to look on top of the wing to check that the fuel cap is secure, or to check the fuel level in the tank with a dipstick, or to fuel the airplane yourself. Most fixed-base operators with self-serve avgas pumps stash a ladder by the pump for just that purpose—but you never know. The benefits of fuel located in such a high place mean the fuel can be fed by gravity to the engine, and can be fed from both tanks at the same time.
Many Cessna 172 variants have a step by the cowling, and that’s how you get started. Facing the airplane, put one foot on the cowling step, hoist yourself up, and step your outside foot on the strut—you’ll see the strut step waiting for work.
The step is a simple item—a square of catwalk paint held in place by two metal bands—but it has a part number, which means you shouldn’t try to make one on your own, because it would not be approved for use on an FAA-certified aircraft.
