This tut will show you how to make a sticky piston door, i'm going to post an upgraded version where i'll show you how to build higher and higher, so in the end you'll be able to make a 50high block door like i did
Hope you enjoy
I already knew this and you could do 3 blocks high for each door. / but here's a challenge. IT's easy but I haven't done it. Place the piston upwards so they don't open side ways but 2 blocks go down and 2 blocks go up