It is for some reason possible to clone your doors on Minecraft without mods or hacks. This can save massive amounts of iron bars and wood, and only requires you to make one to start off with.
I will probably make a video some time in the future, but for now I'll stick with a text guide.
1. Put down a sand.
2. Put a cacti on the sand.
3. Facing the block from any side, click the block directly down and to the right or left of the sand block with your door.
4. Instantly, the door and cacti should break.
5. Collect your 2 doors and 1 cacti block.