The paper used for writing brush characters is four feet apart. How far apart are four feet?

Generally, the full size of our commonly used "four-foot" rice paper is 138 cm × 69 cm. Four-foot rice paper, the finished product of "four-foot horizontal cutting" is "Doufang", which is 69 cm long and 69 cm wide; The finished product of "four-foot vertical cutting" is a "four-foot single strip" with a length of 138 cm and a width of 34.5 cm.