How can I make a simple sprite that I can stretch for different platforms?

Hi. I’m currently working on a platformer where all the platforms are styled with outlines like this:
49555-example.png

All the white is transparency btw.

These boxes make up the platforms which obviously need to be different sizes.
The problem is, I don’t know a good way to stretch a simple image like this without distorting it.

Does someone know a simple way that will let me replicate this look on multiple game objects of different sizes?

Please and thank-yous.

Use the following settings

49557-screen-shot-2015-07-06-at-111822-am.png