So, Tap Code: A Simple Grid Guide

This week, (*tap tap*) communicate with a simple Morse Code-like cipher by tapping




Tap code is a simple Morse code-like method to transmit a message—letter-by-letter—with a grouped series of tapping. The alphabet is broken up into letters and organized right to left into 5 rows and 5 columns. The letter can then be transmitted by two grouped taps that designate the letter’s row and column. There is a small pause between row and column with a larger pause used to distinguish between each letter in the message. As the English alphabet by the 20th century has 26 letters to fit into the 25 spaces of the 5×5 grid, the letters C and K are grouped into the same square since they usually represent the same sound.


Tap code is simple to learn and can be taught quickly without having to fully memorize the entire grid. The first group determines the letter in the row (A, F, L, Q, or V)*, then a smaller pause before the second tap —between one and five—that determines which letter in the row. Since the letters are transmitted by row, then column, the letter R is as 4 and 2. Where, four taps for the row (A…F…L…Q) are followed by two taps for the column (Q…R). To increase readably, sentences can be further broken up by the less common letter X (5,2) in the place of a period




Tap code is typically sent as taps or knocks (also known as “Knock Code”). However, the simplicity of the code allows the messages to be sent as part of any simple grouping of signals. This includes the flashing of the lights, the beats of a drum, tapping on an arm or leg, chopping wood, whistling, or the controlled sweeping of a floor. Codes can even be stored and preserved into a physical environment with groups of knots, rocks, or stitches. 


Historically, tap code was used by prisoners and POWs during the 1900’s separated by cells. Prisoners could hold entire conversations by tapping on the bars and walls between cells. Tap code’s grid structure can be historically traced to the Polybius Square from the 150 B.C.E which used the Greek alphabet. before its adoption into English. Since physical messages can be intercepted and most codes are difficult to teach, tap code can be a simple alternative


Quick Reference


Since the messages are transmitted letter by letter, some important words can be shortened to translate quickly


SOS: (4,3) (3,4) (4,3)


Error: (1,5) (4,2) (4,2) (3,4) (4,2)


Wait: (5,2) (1,1) (2,4) (4,4)


Yes: (5,4) (1,5) (3,4)


No: (3,3) (3,4)


Repeat: (4,2) (1,5) (3,5) (1,5) (1,1) (4,4)


Ready to Receive (RTR): (4,2) (4,4) (4,2)


End of Message (EOM): (1,5) (3,4) (3,2)


Goodnight (GN): (2,2) (3,3)


Good morning (GM): (2,2) (3,2)




Numbers are transmitted in several possible ways. Numerical values can be spelled out where “2” is written out as “two”. If previously agreed upon, numbers can also be communicated by slowly tapping out the separate values where 32 is (3,2) and 127 is (1,2,7). Here, the number of zero is written as the letter O (3,4). In addition, numbers can be written 0-9 in a 6×6 grid and sent in the same method as letters




*Mnemonic for AFLQV (Always Fly Low. Quiet!—Velociraptors!)