Possible, but you've gotta make sure it only touches at a single point (in which case it will tip one way or the other, because nothing's perfect). If you draw it a little too low, it'll intersect the triangle two places; now it's rigid (or close to it). Draw the lever a little above the fulcrum, so it can settle down on it. Also, since it will fall one way, make sure it starts the way you want by making that side just a hair longer, then it will easily flip up when you drop the weight on it.