I have an exerciser step I use. it has 4 independent feet I can use to adjust the height.
I do not need it often however I have an adult handicapped daughter and I need a good solid base step for her. I bought it on sale while looking for something else. Cost about $20.
I got thei portable step at an RV show. It has two heights; one with the legs down (as shown) and with the legs folded - where it gives about 3" height.
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Gale & Hank- 2012 Berkshire 390BH