The tightening mechanism relies upon captive nuts held in place by. They have a good foot structure that cradles with just the right amount of arch. For those who arent familiar with what this is, its a simple strap that you loop over your bike rack and run it to your trunk lid to take some of the stress off of the hitch/rack. After reading a lot of reviews about OneOdio, I decided I had to try one of their products. I have nothing to lose if it did not work out. They are a bargain for what you get. It would be nice if they included instructions in the box, but as I have mentioned, there is Youtube. Not happy at all and I believe it to be a design fault, so I am reducing this to a ONE star and will advise AVOID this product. 試してみて、欲しい人に譲りました。コレを使ってまでair podsを使うならリード付きを買った方が良い。 There is definitely a front crossbar and rear cross bar but they aren’t labeled so it was a trial and error installEnd result is flawless ❤️