Tutorials/Secret door

Fishing in lava door
Firstly, build a 5x3 Lava pool. Then, place a wooden pressure plate somewhere in the lava. Stone pressure plates do NOT work! You must be able to remember where it is located. 2 Blocks below the pressure plate, run a redstone wire to a secret piston entrance. This is because you can fully conceal a secret piston door in a flat wall.

Secret Painting Door
Start by making a 1x2 gap where you want your doorway to be. Be sure that the wall area around the secret doorway is big enough for the size of Painting you want. For example, for a 2x3 painting, you will need 2 blocks on both sides of the secret doorway, because the doorway counts as 2 blocks. The painting will not stay on the wall unless you follow the next directions carefully: First, place a solid block in the bottom of your doorway, and in the top section place a sign.

To put up the painting in the right spot, look at the lower left-hand corner block of where you want the painting and right-click on that block (hint: you may need to replace the painting a few times to get the right size).

A way to make the doorway easy to enter is by making a 2x2 hole and putting four signs on the side, then use the sides of the signs to put up a 2x2 painting, allowing a bigger hole to walk through.

There is a second method to this as well. Simply place a regular door into the wall, they can be single or double doors. Open them and then place a painting as you would regularly do. The doors register as full blocks, so the painting will go over the door seamlessly. The important part is having the doors be open, because there is no way to open them through the painting. The doors can be powered by redstone to form a solid wall upon first inspection, then open up to reveal a hidden room with the push of a lever, pressure plate, or button.

Piston Hidden Door
For a door that is completely hidden except the lever/Pressure Plate/Button to power it, you can use a Piston door. A very simple version is one that just moves 2 blocks to the side with 2 Sticky Pistons, which are hidden inside a wall and are powered by Redstone. To make some more complicated and fancy ones, you can get the blocks to move first away from the Player, and then sideways, allowing for 2 wide doors and it also allows you to build it so that the door appears at the middle of a wall, instead of it only being possible to make it either in a corner or in a tunnel of the desired width of the door, because now all the pistons are behind it. You have to do some redstone wiring, though, and if you want to make the door 2 wide it will need at least 12 sticky pistons, 4 to move the blocks into the wall, 4 to move them sideways, and 4 to move the four pistons that moved the blocks sideways sideways. You have to make the delay from the input to the first four pistons, the ones that move the blocks into the wall, 2 ticks. Then split the redstone wires that go to the other 8 pistons; one way has a delay of 1 tick, the other one a delay of 4 ticks. Then after the delays you can join the wires again and bring them to the pistons. To make it more hidden, replace the blocks with bookcases. An example of this can be found here.

Underwater Hidden Door
Doors and entrances can actually be hidden underwater. This is accomplished via the use of water blocking objects such as trapdoors, ladders, signs etc. Many players prefer to hide these underwater entrances in man-made fountains, bodies of water or behind/in waterfalls. When creating an entrance in the base of a body of water dig a small hole, 1 block only is hidden the best. Then place a ladder at the entrance of the hole, you should see that this will block out the water, leaving an air pocket. You can now continue this ladder shaft down into your base. Be careful when placing torches or light sources to not make this hole easily noticeable.

Lava Door
Minecarts can be used to teleport through lava, and your player will instantly be inside the minecart without actually having to go through the lava. This can be used to your advantage. First, make your doorway (at least 3 layers) of blocks as the door frame. Then place one minecart rail on the floor outside the doorway directly in front of it, and another inside, directly behind your doorway. On each of these rails, place a minecart. Optionally, half steps may be placed around the rails to keep the minecart from being pushed. Remove one block from the top middle layer of the door way, and remove one directly below this hole on the floor as well. Then get a bucket of lava, and place the lava into the top gap inside the doorway, being careful to move out of the way immediately to avoid getting a faceful of lava. You can now use your Lava Door by clicking through the lava to the minecart on the other side.

Lava and Water Entrance
This entrance is dangerous, as the player is required to go into lava briefly. In addition, it is impossible to exit. Dig a 1*1*5 hole in the ground. Place a sign inside the hole, 1 block below the opening and 3 blocks above the bottom of the hole. Place another sign one block above the bottom of the hole. Fill the lower 1*1*1 gap fully with water, and fill the top with lava. The signs hold the water and lava in position. When you enter, you fall through the lava into water, then into a 1*1*2 hole. You can use this to continue building a passageway.

OPTIONAL: Build a 5*5 hut around it with a door, with a sign labeled "Trash Deposit" to fend against anyone thinking that there is a secret base in there. The lava will also trick them!