Those look like a homemade version of the Weldbilt 3-piece dollies just a heck of a lot lighter😁. If memory serves me, you would lift one end of the vehicle then assemble the dollies & roll them under the vehicle. Then lower it onto the dollies & hook the vehicle from the other side & off you went. Some of us back in the day used to cheat. hook & lift one end up high & using jack stands put far back on each side roll the dollies under. Then lower it & pull the stands out & off you went.