RV Pro RVP140842 scissor jacks help stabilize trailers and RVs when idle. They the trailer from rocking back and forth. Extending scissor jacks require a 3/4″ Hex socket on a drill, or use the manual handle that’s included. Once the jack reaches the ground, lift the trailer approximately 1/2″. This will apply adequate pressure to scissor jack. Select the correct length and weight capacity when replacing existing scissor jacks.