I absolutely love these things and have used them for a couple of years. I enjoy wandering around with my kids and having them put it up to just about everything. ("Dad! this has a golden mean in it as well!" — I'll never get tired hearing that). You can also use them to bring some simple relational beauty and balance into anything physical that you make.
You can go to this website for some very well made ones (and a little pricey) or just download some plans for a few bucks and make your own. — Eric Warner