1. The problem statement, all variables and given/known data [PLAIN]http://img823.imageshack.us/img823/6601/unledpicturex.png [Broken] 2. Relevant equations [itex]q = \tau/b[/itex] [itex]\tau = (VQ)/(Ib)[/itex] I would like to calculate the shear flux in one row of nail. By taking the first moment for the upper board, calculating q and dividing by 2 I get the correct value. My question is the following, why can't I take for example the left board? I would get Q=0, but what is the physical meaning of this? Why can't I use the left or right board to calculate the flux in the nails? Thank you.