Clue or key: the word “by”.
~
You didn’t fail, not really.
Your two by four entry is incorrect. It has to be a repetition of the first word of the phrase.
Five by five is a military communications term referring to how loudly and how clearly a radio message has been received. A scale of one to five for each element, ranging from lowest to highest, indicates tells the sender whether or not the message needs to be sent again. By transmitting “five by five”, you are saying, “I read you loud and clear” (technically and grammatically loudly and clearly, but I digress). By transmitting numbers lower than five, the recipient tells the sender what failed so that it can quickly be rectified.
~
By definition
Standing by
By and by
By virtue
By the wayside