Tap Code / Knock Cipher
Encode and decode using tap code (prison knock code). Each letter is represented by row and column taps on a 5x5 grid.
Tap Code Grid
C and K share the same position (1,3). Z is at (6,1).
Examples
A = . . (row 1, col 1)
H = .. ... (row 2, col 3)
S = .... .... (row 4, col 4)
Z = ...... . (row 6, col 1)
Tap Code (Knock Code)
Tap code is a simple cipher used to communicate through walls or surfaces by tapping. Each letter is encoded as two groups of taps representing its row and column position in a 5x5 grid.
History
The tap code gained fame as a communication method used by POWs, particularly during the Vietnam War. Prisoners would tap on walls to spell out messages letter by letter.
The Grid
The standard 5x5 Polybius-style grid places letters A-Z with C/K combined to fit 26 letters into 25 squares. Some variations extend to 6 rows to give Z its own position.
Use in Puzzles
Tap code puzzles may appear as:
- Audio recordings of tapping sounds
- Dot patterns representing taps
- Number pairs (row, column)
- Physical puzzles requiring knocking