This is the B&W companion. It is a 5th whell hitch that locks into the B&W turnoverball receiver. The setup is such that you can lay a rubber mat (or bedliner) beneath the feet of the hitch to save your bed. When not in use, there are no rails left in the bed.

The only thing about the B&W hitch that isn't 100% flat are the safety chain hook points... they stick up about 1/4 - 1/2" from the crests of the bed ridges.

The B&W is also a 100% bolt on accessory. There are 2, 3/8" angle iron rails that rest on the frame. These rails support the center member that holds the tounge weight. The rails are clamped onto and bolted to the frame on both sides. Installation takes around 3 hours...less if you know what you're doing.

If you have older trailers with the pin-through type tounges, B&W makes inserts for these trailers, too.

As per B&W, there is no clearance issue on 4x4 trucks. 4x2 F250s have a slight issue because they have no block on the rear axle (I have one of these). This issue is only when heavily loaded and the ball is turned down. Four solutions... 1) install F-350 blocks 2) leave ball up if possible 3) remove ball while loaded 4) B&W sells a blank insert for this clearance issue.