I just went to check the photo in the link mentioned here and it is a square (I counted the 1/2 square triangles on the borders and there are 21) but I have seen one where borders were added to top and bottom to make it rectangle for a bed.
Originally Posted by DebraK
I found this one at Quilters Cache. It's called "Carpenters Wheel (Easy)". You can find a link to the picture on page 2 of the pattern. Maybe it is square , and just photographs as rectangle, but I bet you could figure out what to do looking at the picture and possibly graphing it out.
http://www.quilterscache.com/images12/kayesCW.jpg