In this paper, results from a model capturing the knowledge from a human being are presented. The model is built to develop a Knowledge-Based System (KBS) in the first stage of analysis of the system's life cycle. The model arises from the difficulty at which a knowledge engineer faces when useful information from an expert is to be captured and stored. The model integrates elements from human thinking going through perspectives of the reasoning cases and the knowledge engineering. The model has been validated and implemented in Colombian small and medium companies (Pymes) in contexts which let to extract knowledge from experts in specific domains.