All you need is a Sewing Gauge. You could use a ruler as well, but I found this easier.
Once you place your tape where you want it, take your sewing gauge and measure out the distance that you want it. Now as you go around your jar, you can make sure that you keep the same distance apart from the other tape. No more crooked tape!!!
Also, if you would like to see how to make the flowers that I added to the jars, click here.