So this is what I want.
Two sticky pistons, one at left side and one at right side so that there would be one empty block's space between them after both have had blocks added and in inactive state.
Simple thus far! But next bit is harder. How can I make them so that they are in active state, filling that one block's area passively and would pull back, revealing the one block's free space that would be a door when pressing activator like pressure plate/button (one time short duration activation)?
In basic, a closed "door" that would open with activation.
I've tried everything I can imagine and tried to look from Google but haven't found anything that would help and only can make it so that pistons are inactive, leaving the door open until walking upon the activator which would close it. (Not the effect I want! D