I have no idea why, but I just tried to place a torch on a Wooden Door, and for a frame, it shows a 2x2 square that is Purple and Black. It is different when you try to place the torch on the top, and bottom of the Door. Also, to make it more clear, you have to build something like what the screenshot below shows, so that it's easier to understand, if you're having trouble trying to do this. Anyway, when you put the torch on top of the Door, the top part of the Door makes a square like I said before, and gets placed on the left side of the Door. However, if you put the torch on the bottom part of the Door, then it shows a model for the Head item you can obtain in the Creative Mode inventory, and then the torch appears on the left side of the Door. I hope you found this very interesting.