Hmmm, not exactly sure what your question is. Do you want info on how to miter a border? Here's a tutorial:
http://www.quiltingboard.com/t-47911-1.htm
If you want to join shorter pieces to make a longer strip here is a link that actually is about binding, but the first few photos show how to join strips using a diagonal seam.
http://www.quiltville.com/binding.shtml