Remember all those basic consonants where I told you there were 2 possible pronunciations and we'd explain it later? This is later. The rules require understanding what Pat'chim are (Read Complex Blocks if you don't).
 

The letter ㅂ is pronounced "p" in the initial position and as Pat'chim. In other positions it is pronounced "b". So in this example the first instance is pronounced "p" but the second is pronounced "b".
 

The letter ㄹ is pronounced "l" as Pat'chim. In other positions it is pronounced "r". So in this example the first instance is pronounced "r" but the second is pronounced "l".
 

The letter ㄷ is pronounced "t" in the initial position and as Pat'chim. In other positions it is pronounced "d". So in this example the first instance is pronounced "t" but the second is pronounced "d".
 

The letter ㅅ is pronounced "s". Except when it comes before the vowel ㅣ and is pronounced "sh". So in this example the first instance is pronounced "sh" but the second is pronounced "s".
 

The letter ㅈ is pronounced "ch" in the initial position and as Pat'chim. In other positions it is pronounced "j". So in this example the first instance is pronounced "ch" but the second is pronounced "j".