Here I have a weight.  As you can see, the weight is resting on a table.  It is at equilibrium.  I know this because there is no acceleration.  Because it is at equilibrium, all the forces in a force diagram would balance each other out.  At the moment, there are only two forces that would be drawn on a force diagram for the weight.  Natural force and mg.  These forces should balance each other out.  This is a 3 pound weight which means it is roughly 1.36 kg.  Therefore, the mg should be 13.328 N.  This means that the natural force will also be 13.328 N.