I built two frames out of 2x4s, 2 feet wide by 7feet long.(if I had to do it again, I’d use 1x2s .not as heavy). Sorry you'll have to make the metric convertions. Make sure you use plenty of center bracing for your frames .then I Screwed OSB on top. Then I drilled holes on the inside of each frame, and bolted them together, with eye bolts and wing nuts (Used eye bolts so I could pull them apart easily). So now I had two halves, 2 feet wide bolted together. This makes it easier to store in the truck. Then to hook them onto the tailgate, I used one inch wide flat stock metal and bent them to fit between the tailgate and the bed. This way they won’t back off on you when you load your sled. Then I bolted the other end of the flat stock to the bottom of the frame. I used wing nuts hear so I could remove them for storage. I only used two pieces of flat stock ( one on each side of the ramp when bolted together) , but if I had to do it again, I’d use four(one on each side of the 2 foot frames) this would make it sturdier . Worked great and still does if I want to hull three sleds, but it still doesn’t replace the trailer. If I can, I’ll post some pics. I used some stuff that I had laying around, but I think I had about $30 in it.