From The K Language Wiki
Supported in K9

The cut primitive partitions the array y before the indices given in array x.

The portion of the array before the first index is ignored.

Indices must be given in ascending order.

 0 4_"feedface"

 3 5_"adfdsfsdfa"

Repeating indices add empty cuts in that location:

 0 2 4 4 4_"abcde"