Abstract: Holding members for engaging the corners of base plates of nail plates while wooden beams are force down on the upwardly projecting nails to form a truss are made of resilient plastics material of about the same thickness as the base plate and provided with a self-adhesive surface for fixing them relatively to a preparation table. Each holding member is formed at one side so as to lie against the edge of the base plate at at least two points respectively on both sides of the the associated corner. A comparatively thin supporting layer of harder material may be secured on the upper face or between or on both faces of the resilient material.