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Mathematical knowledge for teaching is a part of the knowledge that mathematics teachers must possess. This article aims to describe the prototype of mathematical knowledge for teaching based conceptual (MKT-C) teachers in quadrilaterals. This study used descriptive qualitative method. The subject of the research is junior high school math teachers. Data were obtained using vignette that has been validated by the expert. The results show that the teacher's MKT-C prototype on quadrilateral is not yet ideal. Because the findings indicate that the CCK-C protocol is a quadrilateral category: false and true (incomplete), whereas CCK-C classification is the quadrilateral: false. Prototype SCK-C quadrilaterals category: false and true (incomplete), while SCK-C classification quadrilateral: incomplete and complete. Prototype KMH-C category quadrilateral: do not know and complete, KMH-C classification quadrilic: not found. Knowledge of mathematics for teacher-based conceptual teaching needs to get serious attention because it has not led to an ideal outcome. To achieve the mathematical knowledge for ideal conceptual-based teaching, the main process is required through individual teachers because knowledge is strongly influenced by existing schemes and beliefs that teachers have. This research can be utilized as a model for the development of professional teachers.

MKT-C, CCK-C, SCK-C, KMH-C, quadrilaterals