I can't take credit for this. I Googled "toothbrush t-shirt rugs". I followed the tutorial and had nothing but fun with this project. A little hint, don't use t-shirts that have a large decal covering the front or back. This will not stretch into the "yarn" .
She said the tutorial was on Google.
Here's a link to the project. There is more than one way to make these rugs- some are crocheted. Here's the link- www.dutchhollowacres.com/
where are the instructions to create a t-shirt rag rug