If the internal matrix is stacked with multiple “levels” a single level may be dumped as a square output .ufm file, an operation referring to as “cutting” a matrix (option 11 along with 12 and 13 to set the level/block). See 10.4.3 for the reverse procedure to “paste” a square input matrix into a single level.
The same option, plus others, is also available as described in 10.17.