Snarf files are the clipboard standard for Varvara software.
A .snarf file contains a clipboard buffer, programs will handle clipboard operations by writing to that external invisible file. You can see support coverage here.
The cut operation deletes the selected text from the screen and puts it in the snarf buffer, snarf copies the selected text to the buffer without deleting it, paste replaces the selected text with the contents of the buffer.
( snarf ) @snarf-txt ".snarf $1 @edit-copy ( -- ) ;snarf-txt .File/name DEO2 #0100 .File/length DEO2 ;buffer .File/write DEO2 JMP2r @buffer $100
Snarf is the term for Copy on the Plan9 operating system. The operation is not to copy but to snarf. It's called snarf because snarf is what it does. There is no design document.