1. The problem statement, all variables and given/known data This is a real world application. I am posting it here to follow the guideline for any "coursework-like" questions, but since I have no formal training, I'm not sure what category this would actually fall under. Any recommendations for a more specific posting location would be welcome! I have a cantilever beam in static equilibrium, with a known mass and center of gravity. It is supported at one end by contact at three points inside an irregularly shaped cavity in a wall. My task is to find the force(s) present at each of the points of contact, which have known coordinates and a known normal direction. For better visibility, the image below only shows the three relevant surfaces (brown disks) of the cavity, where they contact spherical protrusions on the beam. 2. Relevant equations 3. The attempt at a solution If friction at the points of contact is zero, then I can easily solve for the unknown forces (red arrows) at the points of contact by using translation and/or moment equilibrium equations, since the direction of the force at each of the points of contact must be normal to the contact surface, and I therefore only have three unknowns (the magnitudes of the forces). However, in the actual scenario, friction IS present between the beam and the cavity at the points of contact, and here I run into trouble. I am conceptualizing the frictional forces as a vectors originating from the contact points and tangent to the contact surfaces, but since they could also point in any direction on the contact surface, I now have nine unknowns and only six equations of equilibrium from which to find them. What am I missing here? It seems like the system must have a unique solution.