Double patchim means that two consonats are piled up. 12 kinds double patchim exist like following. 

Patchim	Pronunciation	Sample
ㄲ	ㄱ k	꺾다, 닦다, 볶다
ㅆ	ㅅ t	있다, 했다
ㄳ	ㄱ k	품삯, 몫
ㄵ	ㄴ n	앉다
ㄶ	ㄴ n	많이, 않다, 괜찮아요
ㅀ	ㄹ l	싫어, 뚫다, 잃다
ㄾ	ㄹ l	핥다, 훑소
ㅄ	ㅂ p	없다, 값지다
ㄺ	ㄱ k	낡다, 읽다, 닭고기, 늙은이, 맑음
ㄻ	ㅁ m	닮다, 젊은이, 닮고
ㄿ	ㅍ p	읊조리다
ㄼ	*	여덟, 짧다, 넓다, 얇다

 

"ㄳ", " ㄵ", " ㄶ", " ㅀ", " ㄾ", " ㅄ", the two patchim piled up different consonat are pronunced on the left side. On the other hand, "ㄺ", " ㄻ", " ㄿ", are pronunced right side. 

*The way to pronunce the last patchim "ㄼ" is following. 

In case of a word which includes this patchim is a word as adjective, it should be pronunced on the left side. But a word is as verb, we have to pronunce it by right side.