Your trailer jack is sitting on the ground and the mounting plate is bent, rusted, or missing hardware — and the jack itself is fine, you just can't attach it to the trailer tongue properly. A bad base plate means the jack won't stabilize and you can't hitch or unhitch alone. Zinc-plated trailer jack base plate kit. The base plate distributes the jack load across the ground and provides the mounting surface for bolt-on trailer jacks. Zinc plating handles the outdoor and road conditions that trailer equipment faces — moisture, road salt, and mud — without the immediate rust that bare steel develops. The kit typically includes the plate and mounting hardware needed to attach a standard bolt-on jack to a trailer tongue. Standard on farm trailers, utility trailers, and boat trailers across nor Stocked at Crofton Lumber and Akron Lumber.