The traditional way of defining text blocks and copying them has been
provided by the alt-F4 (BLOCK) key (see AF4?).
The same tasks can be carried out by the rightmost mouse button (RMB).
Simply start definition of a block by clicking its upper-left corner
by RMB. Then click the opposite corner (lower-right) by RMB.
Thereafter the block area will be seen as painted.
To put the block to the clipboard, click any point inside the block by RMB
or
to make copies of the block in the current edit field, point a new
(empty) place by the mouse and click by RMB.
This procedure may be interrupted at any stage by the DEL key or
by clicking the prompt line (below the last visible edit line).
Another option for the rightmost mouse button is
C = Copying single 'words' by mouse buttons
M = More information on the mouse
Help System (web edition)