What inexpensive techniques are used to create perfectly square tenons in oblong stock?

Question

I would like to insert horizontal pieces into perpendicular dadoes, in order to create simple rails and styles around floating panels for (semi)rustic cabinetry, but I'm having trouble keeping such long pieces square.

Answer 1

http://www.woodshopdemos.com/2blade.htm

Answer 2

I am sorry. I am having trouble understanding this question. Are you having problems keeping the rails and stiles square? That can be corrected by cutting accuracy, and proper sized lumber. The floating panels inside do not have to be square, as long as the sum of the angles offset each other. This can usually be done by "eye", accurately sizing only the last piece.
Hope this helps some...keep trying.