The purpose of this study is to consider flapping of English stops within a word in different aspects of approaches. First, for specification of accurate environments of flapping, we review a few types of rules and contexts of flapping from stress, syllable structure, and foot, and then suggest a modified version of the flapping rule. In addition, for the purpose of surveying the existing analyses of flapping, this paper reconsiders flapping based on resyllabification, ambisyllabicity, and prosodic rule applications. Finally, to show the explanatory superiority of the level-based approach, this paper compares rule-based and syllabification-based approaches with a few examples of the occurrence of flapping.