Easy DIY: Instantly look at your old fence in a new light. Using new marbles, determine a drill bit size that will bore a hole just slightly smaller than your marble. You want it to press in snugly to help it stay put. No adhesive needed. Drill test holes in scrap wood to help you get the right sized holes made. Then go to town. Poof, your old fence looks great and provides cool lighting to the back yard!