... that thing on the front of your trailer that lifts the coupler off the hitch ball. Be sure you don't over crank the jack when lifting the couple off the ball. There are two gears at the top of most jacks and they are held in place by steel roll pins going through the crank handle and main shafts. When you over crank them at the top of the lift range you can shear the roll pin and render the jack useless. Please be careful when at or near the top or bottom of the crank range.