(Part of) Senior Thesis as Writing Sample?

[alephnull]

Heyo! I'm a rising senior who will be applying to grad schools in the next cycle. I'm yet to start on my honors thesis, and will not complete it by the time I apply but I'm wondering if it's common for people to use excerpts of their senior theses as writing samples? If you've done this, how did you go about it? 

[gughok]

It's definitely common - just try and select a self-contained excerpt with a significant argument as the thing you choose to submit. Don't send something that's mostly exposition, or something that's far too long. If you do the latter, include instructions for which parts are important to read, and which parts should be skipped, where the former add up to whatever length limit the school has imposed. If you wanted to, you could mention in your cover letter that you're submitting an excerpt of your thesis, and that whatever position you're presenting there will ultimately be expanded upon (but again, that's no excuse for an incomplete product; whatever you send in should be freestanding).