This work aims to provide a mechanical model for the Propagation Saw Test (PST) based on the Euler-Bernoulli beam, allowing a description of the slab and weak layer stress states in the quasi-static regime. We assume an elastic-perfectly brittle model as constitutive law for both the snow slab, which can fracture for high tensile stresses, and the weak layer, which can fail under compressive or shear stress. The stress evolution is mainly determined by the crack length, which is, initially, created by the saw and, subsequently, increases due to weak layer failure in case of self-propagation. Thanks to the proposed method, the two main test outcomes-full propagation (" END ") and slab fracture (" SF ")-can be found as observed in field experiments. Moreover, the PST parameters can be studied separately, providing a powerful tool to understand the dependence of the outcome from numerous quantities in the test, both geometrical and mechanical.