A mounting pin and plughole arrangement is disclosed include a plughole formed on a circuit board, and a mounting pin downwardly extending from a frame body and having a shank with two hooked portions for fastening to the plughole to lock the frame body to the circuit board by: inserting the shank of the mounting pin through the center of the plughole and then rotating the mounting pin through an angle to force top locating blocks of the hooked portions into engagement with retaining holes that form a part of the plughole.