Since I finally revealed my Marendar moc I can post an instruction for transforming rocket boots/ iron man legs.
When Idea to make legs came to me I was utterly suprised I could not find any pictures on google which I could use as starting point.
So if you want your Moc to have transforming rocket legs, here is a version I made from G1 pieces.
Basic skeleton inside is just a long light grey axle that goes through two toa hands. Then using two pin axle connextors and triangle looking pieces which name escapes me at the moment one can attach rocket boosters below
There is a locking mechanism that uses a black lightsable bar and axle connectors. One can easily use blue/black axle pins instead and any piece that has a pin hole to work as a lock.