What is a tongue or draw-bar on a tractor trailer?

These are items you would be more likely to find on a farm tractor than on a tractor-trailer. A tongue is mounted to the frame (or an auxiliary arm), and can facilitate a hitch or mount for pulling a trailer. A drawbar is the bar which extends from the tow vehicle (or another trailer) to a dolly under the front of a trailer.

You're not likely to find a tongue on a tractor-trailer. The primary means of coupling is the fifth wheel, and some tractors may additionally be equipped with a pintle mounted on the back of the chassis. Drawbars are more common to dump trucks which transport pup trailers behind them, and doubles combinations which require more significant separation of the two trailers than what a typically A-congear provides.