Ashton and I came up with a visual system to communicate under the table, which we called the Alphabet Matrix. We had started brainstorming auditory methods, but realized that they were easy to mess up. Our solution was a visual  system,  but due to the requirement that it must be underneath the table, the possibilities were very limited. We debated sitting on the ground to open up the potential of facial expressions and gestures, but this still seems overly complicated and still easy to confuse.  We came up with the complete alphabet taped to a bar underneath the table which the communicator can tap with their foot. Each letter is written twice, one facing each side of the table, so that the receiver and communicator can easily decipher each letter. We included a space to separate  words  along with a question mark which the receiver taps once to have the word repeated or twice to repeat the entire phrase or sentence. It is up the pair to decide on how formal the words should be and what abbreviations can be used.  This seemed the simplest method that can still convey whatever the communicator wishes. The only miscommunication that can occur are if the receiver doesn't understand the word, but he or she can simply tap the ? to have it repeated.