Lifting a heavy block slightly (perhaps to pass a rope round it) can be achieved by driving a wedge underneath it. A wedge is like two inclined planes back to back. But instead of moving a load up the plane, the plane is pushed past the load to move it. Driving a wedge into a crack, for example, exerts a tremendous force. A hatchet or an axe uses this principle, as do chisels, ploughs and pneumatic drills.