@Justin Roach,
***updated with pictures showing underside***
This rack was built to fit a 2016 4Runner utilizing the factory roof rails.
The short version of how I did mine is;
Using 1"x 2" 16 gauge rectangle tubing, and two pieces of 1" inch angle iron, I made the two cross bars to sit on top of my factory roof rails. The bars are attached to the roof rails by an insert I made to fit into the channel on the inside of the factory rails. Basically a piece of flat stock with two 1/4" bolts welded on. The finishing cap on the ends of the cross bars are some eBay finds.
Next, I purchased a Harbor Freight Tri-Fold ATV ramp. I removed all the hinges and tailgate supports, which left me with three separate pieces. Then using my chop saw, I cut off one section of the three pieces of the ramp to shorten it by about 12-16 inches. Then I clamped all three sections of the ramp together so that the gaps where the hinges used to be, were closed up. This gave me a smooth surface on both sides. Removing all the hinges narrowed the overall width of the ramp by 3/8-1/2 inches.
Then came the task of securing the three sections of the ramp to my home made cross bars. I did this with 1/4-20 nut inserts. For this you would need a tool like this but for threaded nut inserts.
http://www.northerntool.com/shop/tools/product_200578285_200578285
Once I had the cross bars centered and evenly spaced, I marked the bottom of the atv ramp for drilling. Using a 3/8" bit I drilled 6 holes, two holes in each section of the ATV ramps where it would lay across the two roof cross bars. Then, using the same pattern I drilled 1/2" holes into the undersides of the cross bars. This was so that I could put in the six 1/4-20 stainless steel socket head screws. I didn't bother capping the holes since they face down.
After all that, I went back and filled all the old rivet holes that I had drilled out with new rivets. Had I paid attention, I could have sorted the three pieces of the ramp so that the outer sides would have needed no rivets.
Then, the last part. I wanted all the cut ends of the atv ramp to be closed up. For this I used 1.5" aluminum angle.They are not water tight, but it looks more finished that way.
Lastly, paint and attachment of the wind deflector and called it a day.....or 5.
*****Disclaimer***** I make no claims to this racks ability to support any weight, Static or Dynamic.
In regards to the pictures, the ones of the rack on the roof of the truck are mine. The picture of the rack on a garage floor was another members rack who posted right below me. I had to look twice myself when you mentioned it.
-Eddie