Extra mass tray for Vernier DTS cart

Add an extra mass tray to your Vernier [DTS cart](http://www.vernier.com/products/accessories/dts-cart-s/). Remove the hook-and-pile/magnet tabs on the cart and fit this mass tray in their place, much like the [DTS Friction Pad](http://www.vernier.com/products/accessories/dts-pad/).

Have something you'd like to attach to a DTS cart? Take this design and modify it!