Four feet square and four feet straight are the specifications formed by cutting the whole paper in different directions.
Four feet square is to align and fold the two short sides of a four-foot block to form two four-foot squares, so the specification of the four-foot square is: 68cmx68cm.
Four-legged straight open, also known as four-legged split, is to align and fold two long sides of a four-legged whole to form two four-legged straight open, so the specification of four-legged straight open is: 34cmx 138cm. It's a paper specification for writing four-foot couplets.