1. The problem statement, all variables and given/known data There are 2 parallelepiped with dimension x,l,h those were united to create a bigger solid with an "L" form ( see the picture ). The solid is isolated and full of water. What's the force that must be done against the top wall, to make the system in equilibrium? Here's the image: 2. Relevant equations Pascal's principle: everywhere the pressure's the same Pressure at the bottom: $P=P_ext+\rho gh$ 3. The attempt at a solution The external pressure is 0 because the system is isolated; so I thought that the pressure against the wall may be $P=\rho g h$ and the Force would have been ( modular ) $|F|= \rho g h \times S $ where S is the section of the wall.. Unlucky this is not the right answer.. May someone help me?