(defun copy-rectangle-to-register (register start end &optional delete-flag)
"Copy rectangular region into register REGISTER.
-With prefix arg, delete as well.
-Called from program, takes four args: REGISTER, START, END and DELETE-FLAG.
+With prefix arg, delete as well. To insert this register
+in the buffer, use \\[insert-register].
+
+Called from a program, takes four args: REGISTER, START, END and DELETE-FLAG.
START and END are buffer positions giving two corners of rectangle."
(interactive "cCopy rectangle to register: \nr\nP")
(set-register register