Blocks of lines can be copied in Vim using ranges, i.e., two numbers separated by a comma indicating the start and end of the block of lines.

Some Examples

To copy line 20-25, use:

:20,25yank

To copy five lines just above the cursor:

:-4,.yank

where the period (.) indicates the current line.

To copy five lines just below the cursor:

:.,+4yank