<< CheckLongLines | Index | CountMatches >>

Comment out multiple lines

Select your lines with VISUAL BLOCK (CTRL-V), then press I to insert before all highlighted lines. 
Next type your comment character, #. Last press ESC.

You can alternatively select your lines with VISUAL LINE (SHIFT-V), then type : s/^/#
This tells the selected lines that you wish to substitute the start of the line with the # char.