This ethnomathematics article focused on the models of knot which is used in the frame of "Rumah Kaki Seribu." The knot model itself was studied mathematically. The results of this study revealed the way Arfak tribal communities think mathematically. This article uses exploration, documentation, interview, experiments and literature studies method. The result showed that Arfak tribal communities used the characteristics of a triangle. It can be proofed by looking at their consideration of the strengths, endurance, and the stability of their Rumah Kaki Seribu.