Trailer Stabilizing Jacks are used to prevent up-ending of semi-trailers when they are not connected to a tractor during loading and unloading operations. Throughout the loading and unloading process it is always recommended to use two jacks, one on each side of the front of the trailer. The trailer must be situated on a flat, stable and improved (preferably concrete) surface, while the jack sits perpendicular to the underside of the trailer. Every jack is built of a high strength steel construction with a flush-type zerk fitting for lubricating ACME screw. A yellow powder coat finish and a reflective collar for visibility at night are both included. Each jack meets OSHA regulations when used with wheel chocks. **The color of handles included with models may vary between red and black**