Align lines in square

Question

There are one square and two horizontal lines.
I need this lines to be arranged in the square dividing it into three equal parts.

Is it possible to do it without messing with pixels?
How can I align lines in the square? And how can I crop them to the width of the square?

From this:

To this (not perfect):

Answer 1

I can think of two ways:

1) Copy the square. Lock it. Paste In Front. In the Control bar (CS5), make the depth of the new square 33%. Drop a guide. Move the new square down so it aligns with the bottom. Drop a new guide.

2) Draw two additional lines. Put one on top of the top line, and one on top of the bottom. LOCK the square. Select all four lines and use Align → Distribute Equally.

Answer 2

Lauren Ipsum has a couple great methods. I'd probably use #2.

Here's a third though...

1. Copy the square.
2. Edit > Paste In Front
3. Double-click the Scale Tool
4. Enter 33.3% in the (non-uniform) vertical field and hit okay
5. Now set as guides - Command/Ctrl-5

This will give you guides at exactly 1/3 positions.

To "crop" the lines the width of the square you can simply move the anchor points in until they align with the square sides.