How can you measure the force you apply to a wall?

How can you measure the force you apply to a wall?

A modified version of Newton's 2nd Law. Consider the pivot point located where the object touches the ground. The sum of the moment (rotational force) around that point must be zero, since the object is leaning against the wall, and not accelerating. So you know that the reaction force from the wall * the lever arm for that force must equal the gravitational force acting on the object * the lever arm for that force. And then you know by Newton's 3rd law that the object's force on the wall is the same as the wall's force on the object.