If you need to comment out multiple lines in Sublime Text 2 or 3, there’s a short keystroke that you can use. First, you need to highlight the block (multiple lines) that you want to comment out, then press Ctrl + /. You can press it again to toggle on and off.

Line 1
Line 2
Line 3

Pressing Ctrl + / will comment out the highlighted block.

#Line 1
#Line 2
#Line 3

Press Ctrl + / again to toggle it back.