G-Force Hydraulic jars use a piston (metering device) and oil to create a time delay. Once the energy is stored, the jar piston bypasses (step), creating a hammer-and-anvil effect that imparts an impact load to the end of the tool assembly.

As the jar is pulled in tension, a piston moves through a restricted bore containing oil. this process enables the system to store energy and the continued upward pull moves the piston over the step, which releases the stored energy and allows the mass to rapidly accelerate to the top of its stroke. this process creates an impact force that can be twice as great as the tension that can be pulled on the tubing alone.