if you made the copy in block mode, the paste will be in block mode. for instance:

here
is
some
text

if you select those four lines in line mode, then try to paste beside them, it
won't work (even if you're in block mode for the paste). but if you grab them
in block mode, then when you paste (even if you're not in block mode), you get:

here here
is   is
some some
text text

(exact key sequence:
ctrl+v
block-select from the top left 'h' to the bottom left 't'
y
position cursor on 'here' line
shift-A
<space>
<esc>
p
)