8. Spans
A span refers to a set of contiguous columns (colspan) or rows (rowspan), and consists of two values, the start and end values of the set, separated by a colon. Spans are only used by the format, hide, and show commands.
A colspan may be specified using column letters, or column numbers
preceeded with the letter C (or c).
For example, b:d, d:b,
c1:3 and c3:1 are all equivalent and
specify columns B, C, D.
A rowspan is specified using row numbers, optionally
preceeded with the letter R (or r).
For example, r2:4, r4:2, 2:4,
and 4:2 are all equivalent and
specify rows 2, 3, 4.