Next lay out your line of triangles and sew them to bias tape. Be sure to leave a tail of bias tape on each end so you can tie up the banner if you need to. I accidentally bought single-fold bias tape, but I just ironed it in half to make it work. Then you just sandwich the triangles inside that fold and sew along the top. Here you can kind of see that:
That's it! It really went together pretty simply. And now it can be used over and over again. You can make one of these fabric pennant banners - really!! Go try it!