We took a board left over from the see-saw project for the base. We added a dowel to the center of the base. We put a nail in the pole and hung a ruler on it. Our ruler is NOT balanced so I used tape to attach a dime to the back of each side of the ruler to balance out our balance. One dime is all the way on the end of the ruler and the other is several inches in on the other side. We added cups to each side to hold stuff. I will replace the cups with thicker plastic ones later on. I wanted to use frozen ice cups, yogurt cups, or butter dishes but my children have taken all of them out to our golf course in the back yard, to use for outside building blocks, insect homes, child made ant traps, toys for the sand boxes, the water table, and to use with the paint supplies. We had 50 + cups a month or so ago. The children find ways to make them into toys as fast as we empty a container! I thought this set up would work for now. When the cups break I know T. will go dig in his building supplies and replace them with a better set of cups. One balance finished now we will play with this and move on to wheels and axles. This project is in the book More Mudpies to Magnets. BUT! It does not tell you what to do to make it work if your ruler is not balanced (not that I saw). I could not find a good balanced ruler, my son helped make this project , and we used all left over supplies. I don't know why the book makes it look like a balance will work on first try with a child making it and using supplies like this? Maybe it does say and I just didn't read it. I do have a habit of looking at a picture then trying to make something without reading the directions. Anyway that is how we made it. I think even little children would have fun and learn playing with this. I will let D. play with it once T. is done trying it out. He can make a new one himself if it breaks. It is easy enough for a 7 year old to make with very little or no help from a parent.