In Korean phonology, once the stem final consonant deletion rule is applied, no other obligatory rules can be applied. For example, when verb stem /hulth-/ ‘hackle’ is combined with interrogative ending /-ni/ ‘is it?’, consonant cluster simplification rule must be applied and consequently /hul ni/ is derived. After this application, the 'l' deletion rule, which is obligatorily applies in front of initial 'n' never be applied. Firstly, I define this case as 'the limit of rule application'. In substitute for 'l' deletion rule, the 'lateralization rule' is applied, and so the derived realization come as [ʍuʎʎi](←/hulli/). Secondly, I define this case as 'the alternative mechanism for the limit of rule application'. The 'limit of rule application' occurs when rule application affects the lexical meaning of stem or the grammatical meaning of ending if applied, and then 'the alternative mechanisms' work as not applying any rules or applying rules unexpected. This alternative mechanisms help the listener to recognize the difference between underlying representation and surface representation, and to assume the real underlying representation without changing any meaning of stems and endings.