Creating a clipping mask of strokes?

[LadyJemima]

I'm so used to Illustrator where you can create a clipping mask of anything. I want to create a mask or otherwise clip the green bars below...

....to the hypothetical red box so that I can use the same design on the facing page.

I'm sure I'm missing  the obvious, but how is this done?

[SJRiegel · Accepted solution]

Group your green bars, and then Cut. 

Draw the box in place (no stroke, no fill)

Select the invisible box, and choose Paste Into.

(Don't forget to allow 1/8 inch for bleed at the page edges)

[LadyJemima]

Awesome. Thank you so much! Should have thought of that myself but couldn't put my finger on it. (No bleed needed as these are for web viewing only. )

Thank you again!