Is it ensure, insure, or assure?
pronate pro·nate (prō'nāt')
v. pro·nat·ed, pro·nat·ing, pro·nates
To turn or rotate the hand or forearm so that the palm faces down or back.
To turn or rotate the sole of the foot by abduction and eversion so that the inner edge of the sole bears the body's weight.
To turn or rotate a limb so that the inner surface faces down or back. Used of a vertebrate animal.
To place in a prone position.