Mine came with a bungee to keep them together, but bluegill is right. You'll want some weight on the back for FEL use. You should have turn buckles, that might it be what they're called, they should pretty much hold the lower arms in place.
When I first got my l3800 I was using a category 2 box blade, while it worked it was to wide and the turn buckles barley missed my tires.
Cheapest option, buy a good bungee cord.
Second option, buy a cat 1 drawbar.
Best option, buy an implement like a box blade or something similar for a counter weight and at the same time it will keep the lower arms from hitting your tires.
Good luck....