Lift eye bolt on part of the tractor frame. It's of proper strength for the job.
The other end goes on to one of the hoops welded to the side rail on the trailer. They show up better on the first picture. The back is from a shackle on the drawbar.
[video]https://www.google.ca/search?q=lift+eye+bolt&client=safari&hl=en-ca&prmd=isvn&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi8uNX6rMnRAhVHyoMKHbGYBegQ_AUIBygB&biw=1024&bih=681#imgrc=OsAqieqYMK_LfM%3A[/video]