Sorry for bumping but here some update: The ToolsObserver helped me to find out, that the ComponentTool (21013 - Maybe something else on Mac it is called onentToo) is activated if a user click on a component in the library. If i would know, which definition or at least definitionname this component has, i could implement an own tool to place the component. Maybe $dc_observers.get_latest_class has a function to retrieve the name, or another variable? Because when i look in the active_model.entities, there are only the existing entities but not the one at the cursor.. i can't believe, that there is no variable or method to get this information. Perhaps i do it totally wrong and there is another simple solution letting the choosen component snaps to specified faces/components (no the snaping in SketchUp is not very useful) frustrating^^

Thanks everybody. Wasn't the solution i hoped for but instead i wrote a name organized system, which perfectly fits our needs. Now there are other problems, hope i can get a solution for them larrywayn