Step one. Acquire 4 sticky pistons.
Step two. Place 2 of the pistons on top of each other face straight.
Step three. Do the same thing but have these pistons face the other ones.
Step four. Make sure that each stack of pistons have a space of 2 blocks in between each other.
Step Five. Place redstone 1 block from the 2 block space between the pistons
Step Six. Place redstone until you get to the 1 piston in each stack (make sure not to go between the pistons)
Step Seven. Place lever 1 block from space between pistons where you started the redstone wiring.
Step Eight. Place 1 block behind each first piston in the piston stack.
Step Nine. place redstone on top of block behind 1st piston
Step Ten. Make the redstone make a rectangle going out of the opposite way on the side of the first piston.
Step eleven. Connect the redstone in the rectangle from step ten to the first sticky piston.
Step Twelve. Make sure the redstone wiring is also connecting to the block behind the piston door.

Thanks for reading!

(also do same redstone wiring on the other side of sticky pistons!)

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