We pull a Rockwood 5-er with a short-bed RAM dually and we use the wedge so we wouldn't take out our rear window on tight turns. We did buy a custom wedge though made specifically for our B&W Patriot hitch and replace the generic wedge that came with our Rockwood. Rockwood has to provide a generic wedge since there are many brands of fifth wheel hitch.
Mr. Towed: The wedge mounts around the trailer hitch pin to prevent the trailer hitch from pivoting on top of the hitch (as normal fifth wheels do). Instead, one removes two bolts from the back of the Sidewinder or revolution hitch so that by locking the front kingpin in place, the hitch pivots about 22" further back from hitch pin. This makes sure the nose of the trailer is pushed back about 22" further from the cab on tight turns and prevents it from pivoting into the cab. Here's a Reese Sidewinder ad to explain.