A good way of demonstrating the basic principles of hydraulics is to join two syringes together with rubber tubing to make an watertight seal [see figure 1]. The syringes can be filled with water, oil, or just air. Pushing plunger A causes plunger B to move out and pushing plunger B in causes plunger A to move out. This works even if the syringes are not in the same plane. i.e. if the tubing is bent by 90° as long as there is no kink in the tube that prevents the free flow of fluid.
By adjusting the size of the syringes it is possible to demonstrate how to multiply force [see figure 2]. A small mass on a small syringe can lift a much larger mass if it is resting on a bigger syringe. This is because the pressure in the two syringes is equal, but the surface areas of the two pistons are different, and force = pressure × area.