The 'Step' of Step & Flip is a step ahead, which often (but not
always) is the same as a Press Ahead. 'Flip' means Run into the
adjacent position (as in Flip The Diamond).
Step & Fold,
Step & Flip can be done from any line of 4.
Upon completion of the call, the original Ends are adjacent to each
other. From Parallel Lines, Step & Flip is done in each Line, and
nobody crosses the center line to the other half of the set.