Trusses only take axial forces. Therefore they do not prevent the nodes they are connected to from rotating. In case that only trusses attach to a node, Karamba3D automatically removes its rotational degrees of freedom. Otherwise the node could freely rotate which is a problem in static calculations. As soon as one beam with bending enabled connects to a node the node has rotational degrees of freedom. Bear this in mind when the “Analysis”-component turns red and reports a kinematic system. Transferring only axial forces means that a truss reduces a node's movability in one direction. A node that is not attached to a support has three translational degrees of freedom. Thus there must be three truss elements that do not lie in one plane for a node to be fixed in space.