Lionel 6-29486 P&H Harnischfeger Crane aka 6828 truck crane

I was recently able to find online a new in the box P&H truck crane.  My original was from 1960 and had all but fallen completely apart, and I was anxious to re-add this to my modern layout. If you've owned one, you no doubt know how delicate and easily breakable most of the plastic parts are, but I was able to assemble it without casualties. I was left with extra parts, pictured here, and I don't know what they are for. They are double elastic bands with a bar at then end, and it came with two of them. Are they for securing the truck crane to the flat car?  I choose to display my crane fully assembled.