J.
J consonant sounds uniformly like the soft g, and is therefore a letter useless, except in etymology, as ejaculation, jester, jocund, juice.
K.
Khas the sound of hard c, and is used before e and i, where, according to English analogy, c would be soft, as kept, king, skirt, skeptick, for so it should be written, not sceptick, because sc is sounded like s, as in scene.
It is used before n, as knell, knot, but totally loses its sound in modern pronunciation.
Kis never doubled; but c is used before it to shorten the vowel by a double consonant, as cockle, pickle.