The jack includes a mounting clamp that is designed to clamp onto the tension rails. The maximum distance between rails is about 2 1/16" and the minimum distance about 1 3/32".The L bracket mounts in the front of the rails, while the straight metal back rail is placed behind the rails, and two screws are provided to pull the two pieces together, providing a very secure and solid clamp for the jack. Note that the distance between rails may vary, even on the same banjo. This item is in the category "Musical Instruments & Gear\String\Folk & World\Banjos". The seller is "djangobooks" and is located in this country: US.