I am building a cabinet that is 40" across the back, the right side is 25" and the left side is 8". The front is the resultant diagonal. (It will go in a corner...) There is a top and two shelves; I am leaving the bottom open. It was easy enough to cut the top; I just clamped a straight edge and cut it with a circular saw. I planned on doing the same with the shelves, but am a little concerned about getting them as precise as they have to be with such equipment; if the angle is not exactly the same as the top, it simply won't fit. Then it occured to me that if I cut the shelves a bit oversized and carpet taped them to the top along the front edge (reversing the diagonals of course) they would form a rectangle (or nearly so). If I then ran the whole thing through the table saw, my angles would have to be exactly right; and cutting the right size would just be a matter of setting the fence right.
However, I am a little concerned about running something held together by carpet tape through a table saw. If it pulls apart it could be quite a mess; though I don't see why it should pull apart.
Every try something like this? Any other suggestions to get the shelves to be exactly like the top?