STABILIZE YOUR RV OR TRAILER! The Andersen 'Trailer Jack Block' eliminates nearly all of the movement in your parked RV or Trailer! You will be amazed how solid everything is when using the Trailer Jack Block with your stabilizer jacks! For great results, use two blocks at the front and two blocks at the back of your RV. If you want the most solid and absolute best results on a trailer that has more than 4 stabilizer jacks, use one block per stabilizer. MAGNETS MAKE IT EASY! No more guessing on where your jack pad needs to be! The magnets stick right to the bottom and stay in place! The lipped edge also helps keeps your jack pads from slipping off the block! LESS STRESS!