good days im redoing the big 9 blocks door from mi old mod 
the thing is 
there is a main door block created from the class 

public class base_door extends DoorBlock {  

surrounded by 8 panel blocks created whit 

public class base_sub_puerta extends Block {

if one of the sub panel blocks get clicked it has to search all the surrounding blocks looking for the main block to activate the function in base_door

public static void toogle_door() function 

the thing is i dont remeber how i made it in 1.8 and most of the old code its loss just have some assets and youtube videos 
it was something like 

	if(  BlockState.getBlock() instanceof base_door.class   )
	

 

 

 

How i check if block or item is instance of custome class ? 

BlockState#GetBlock()

at the end was without the class thing 

            if( blkstate.getBlock() instanceof base_door_big  ) {
                center = cursor;
                break;
            }