Super hard riddle!! Dare you to try and solve it!!!

You wake up in a dark room lit only by a single light hanging from a wire in middle of the ceiling. "Where am I?" you ask yourself. Looking around you see windowless concrete walls and that the room is empty except for a wooden table and chair in the center of it under the light. There is a door on the far side of the room beyond the table.

You get up, walk to the other side of the room and try to open the door. Locked. There is a keypad of some sort with a small digital screen and 26 buttons with the 26 characters of the English alphabet just above the door handle. You bang on the door and shout for someone to open it for a few minutes. No answer. You see etched on the door, "The Table Has the Key".

Looking at the table you now see that you missed what was on it when you walked past to get to the door. Looking more closely you see three groups of letters and blanks (denoted by an underline _) etched in the table, and below each group are dominoes numbered 1, 2, and 4. Something is odd about these dominoes though, the pips are in the wrong places. Here's what you see:

c_r ____
·__
|*·|
|··|
|··|
·¯¯
____ __n_h
·__
|*·|
|*·|
|··|
·¯¯
·__
|*·|
|·*|
|··|
·¯¯
·__
|**|
|··|
|··|
·¯¯
_a_io_al ____
·__
|**|
|·*|
|*·|
·¯¯
·__
|·*|
|**|
|*·|
·¯¯
·__
|**|
|·*|
|*·|
·¯¯

Under all three of these groups you see another etching, "The key is in the commonality of the three."

Note: If your web browser butchers the dominoes as in it makes a mess of them, then copy the text into Notepad or Word and set your font to Courier or any other font that spaces characters evenly regardless of what character they are. Also an asterix, "*", denotes a pip, and a centered dot, "·", within the domino denotes a blank space that is supposed to be the same size as the asterix and the ones outside the dominoes are just for cosmetic correction. The centered dots were just my attempt to correct what the default fonts do to regular spaces.