
The marks allow you to mark the beginning and end of a block, and then perform
certain functions on that block. The characters in the block are highlighted.

Select:
    B - This sets the beginning of the block at the cursor position
    E - This sets the end of the block
    R - Use this to unmark the block

Use these once the beginning and end of the block have been marked:
    C - Copy the block to the current cursor position
    M - Move the block to the current cursor position
    D - Delete the block (CTRL-U un-deletes block)
    P - Print the block on a printer
    
    ESC - cancel mark and return to edit mode
