Rules vary from state to state but if the LP cylinder is mounted on the forklift truck you do not need additional placards. The TDG placard is a red 1075 explosive. it must be accompanied by a shipping manifest document. under what conditions you need one escapes me at the moment but a quick google search of TDG (transportation of dangerous goods) should answer that for you. Most truckers who carry cylinders on a regular basis have a LP cylinder cradle mounted to the bulkhead to securely mount the cylinder so it doesn't go flying in a collision. So Keep it lashed down.