Slip proof rug

Any of you have hard wood floors? How about rugs for your hard wood floor? It wasn't until we moved into our current house with hard wood floor, that we needed some rugs. With the rugs came slipping and sliding and constant repositioning. Thanks to Martha Stewart, I learned that you can run lines of acrylic-latex caulk on the back of your rug, and it will keep it from sliding on your hard floors.