Saint Paul, while never one of the apostles, is usually given the respect as if he had been one. Before his conversion to Christianity, Saul of Tarsus had been persecuting the Christian community. After his conversion he wrote many of the Epistles and preached and thus his device symbolizes his new life, the Gospel, being placed over his former life, the sword. The sword was also the method of his martyrdom.
When Christ founded His Church He entrusted to Simon-Peter, in what is called the Apostolic mandate, the keys to the Kingdom of heaven. These keys are placed on an inverted cross because tradition tells us that when Peter was martyred by the Romans, he was crucified upside-down because he did not feel worthy enough even to die in the same manner as Jesus.
Saint Philip's device depicts the symbol of his faith in Christ, the cross, for which he suffered a cruel death. Reportedly when scourging did not silence him, he was stoned, crucified, and finally run through with a lance. The two loaves of bread are to represent his commitment to Christ at the feeding of the multitudes, "Two hundred silver pieces would not buy enough bread for them, even to give each a little." (John 6:7)
Saint John, when represented as an Apostle, rather than his role as an evangelist, is represented by the snake coming out of his chalice. Tradition tells us that Saint John was the only Apostle not to have been martyred and to have died of natural causes at an old age, even though many attempts were made on his life. The most notable attempt was with a poisoned chalice.
Saint James, the Less, used to differentiate him for the other Apostle Saint James, was reported to have been taken to the top of the Temple in Jerusalem and pushed off. After hitting the ground and being grievously injured, he pulled himself to his knees begging forgiveness for those who had injured him, whereupon another of his assailants caved in his skull with a fuller's bat. When dead it is told that his body was sawn asunder, and thus the significance of the charge in his device
Saint Matthias, who was that Apostle elected to fill the twelfth seat vacated by Judas Iscariot, is represented by a battle-ax. It is the instrument of martyrdom for having preached the Gospel in Judea. The ax is placed on the book of Truth for which he gave his life.
Very little is actually known about Saint Bartholomew, except that some accounts believe him to have been Nathaniel, about whom much is said in Saint John's Gospel ( John 1: 45-51). Reportedly, Saint Bartholomew was martyred by being flayed alive before being crucified and thus the reason for the flaying knives on his flag.
Saint Jude, brother of Saint James, also known as Thaddaeus or Lebbaeus, traveled widely with Saint Simon to preach the Gospel, and thus he was given the sailboat to signify his many journeys. There is no record of the manner of his death.
Saint Matthew, when he is represented, like Saint John, as one of the Apostles, and not as an evangelist, is represented by three bags of money reflecting his position as a tax collector when he was called by Christ to follow Him. Saint Matthew is reported to have been crucified on a Tau cross and then beheaded in Ethiopia where he was preaching the Gospel.
Saint Simon, who was the companion of Saint Jude on many missionary journeys, is represented by a fish resting on a book because he was a great fisher of men through the power of the Gospel. The actual method of his death is uncertain but it is believed that he was beheaded for his faith.
Saint Andrew, the first to be called by Christ to be an Apostle, along with his brother Simon, now called Peter, is believed to have been crucified on an "X" shaped cross in Greece after preaching the Gospel there.