It often happens that in a plane truss all joints are not transversely stiffened. If one joint of the compressed girder of a beam is free, the girder is liable to fail by buckling perpendicular to the plane of the truss, between the adjacent joints. The chart given here enables a rapid determination of the critical loading to be made. The compression and moment of inertia are assumed constant along the length of each bay, but may be different in the two bays.