Fun puzzle - connect boxes

[mouser]

From http://boingboing.ne...nnect-the-six-b.html

[tomos]

Clever

[mouser]

Btw if anyone is struggling, this isn't a trick/joke, there really is a solution.  Here's a clue for people who get stuck:

Spoiler

Print out or draw the picture, then connect 1 with 1, and 2 with 2, now see if you can figure out how to connect 3 to 3.

[anandcoral]

Very good indeed.

Spoiler

One shd try on paper instead of screen to understand the solution.