How do you make a hidden door in Minecraft?

How do you make a hidden door in Minecraft? Make a two-block high, two-block wide hole in a chosen wall. Place a three-block tall Sticky Piston pillar on one side of the doorway. Attach a two-block high Stone pillar to the Sticky Piston pillar. You should now have a fully concealed doorway.

Make a two-block high, two-block wide hole in a chosen wall. Place a three-block tall Sticky Piston pillar on one side of the doorway. Attach a two-block high Stone pillar to the Sticky Piston pillar. You should now have a fully concealed doorway.