The line mark is useful for manipulating the text as whole lines. As needed when the margins and/or indentation is to be preserved during a move or copy operation. The line mark is useful for manipulating the text as whole lines. As needed when the margins and/or indentation is to be preserved during a move or copy operation. THE LINE MARK IS VERY HANDY FOR CHANGING THE INDENTATION level in programs or documents via the shift left/right operation. Copying between different files is as easy as copying within a file. Simply mark the text in one file. And then select ANOTHER FILE Alt-L specifies the START/END of the LINE mark. Alt-U UNMARKS any existing mark. Alt-D DELETES existing mark. Alt-M MOVES existing mark to the cursor position. Alt-Z COPIES existing mark to the cursor position. Alt-F7 SHIFT LEFT. Alt-F8 SHIFT RIGHT.