A hidden door is useful in bases and houses to hide you treasure this design is compact and use full.
Step 1: What You Need
40 building blocks
20 pieces of redstone
12 sticky pistons
And one lever
Step 2: Placing the Pistons
Make a tower of two pistons both facing the same way. Then make another two piston tower right next to it facing the same way. Then put another two piston tower directly infornt of the tower in the back. Make sure it is facing towards the front. It will form a v shape then do the same thing two blocks away facing in towards the first v. It will look like the picture.
Step 3: Adding Blocks
Put a tower of two blocks inside the v shape of both sides then put another tier of two blocks in front of them after that put a roof on the structure it will look like the pictures.
Step 4: Adding Blocks Continued
Put two blocks diagonal to each other on both sides' pistons so the bottom block is closer to the front. That is important it will look like the pictures.
Step 5: Redstone Time
If you go ontop of the structure you will see a 2 by 6 rectangle with a 1by 4 rectangle next to it. Put a repeater on the each of the blocks second to the end of the 2 by 6 rectangle the once towards the back should have 4 ticks. Full the rest of the rectangle with red stone it will look like the picture.
Step 6: Redstone Time Continued
Now put Ted stone on The diagonal blocks that you placed on the pistons. Make sure to do this on both sides. After that put a repeater under the top diagonal block. Make sure it is facing away from the lower block it will look like the picture. Remember to do this on both sides
Step 7: Final Step
Now go to the 1 by 4 rectangle that is not covered by redstone on the roof. Build up one block and put a lever on the second block in from either side. The lever will turn the door on and off when you flip it.
Step 8: Hiding It
Make a wall I front of the pistons using the same block you used for the structure. And close the door.