Surf Rack t-slot mounted Pads

I was driving the other day and I saw a truck that had pads mounted on their racks. The pads did not wrap around the racks like all pads I've seen as pictured.


The pads sat on top of the racks. The only way I could think it was mounted was using the t-slot in the rack to anchor it. But I cannot find anywhere, any pads that are mounted using t-slots. I was driving and couldn't get a picture.

If such a thing does exist, it would be cool right? Way cleaner looking than the normal wrap around pads. Anyone know if such a thing? Do you think the owner DIYed it?