You are driving along towing something behind your car. It might be a caravan, a trailer of some sort; it might be related to work or holiday. Your normal vision from your wing mirrors is obstructed and you need to use a set of towing mirrors.
You will find many versions on the market and you need to try them out on your car before you drive. Some are sold with one particular model of car in mind and others fit all sorts. You need to ensure you have one that will suit your car.
You can buy flat or convex mirrors. The latter give you extra width of vision but a stranger perspective and you need to consider which is best suited to you.
The mirrors you attach must be outside the normal side mirrors, but not too far away from the car. Different states and countries have different laws and regulations covering this. You do not want to be looking too far away from the car and you do not want to create another obstacle to fellow road users by having things sticking out the side too much.
The towing mirrors need to be fixed and adjusted for your driving. This means checking that you can actually see them and that they are showing you not only the side and rear quarter, but also some of the area behind the elongated vehicle.
All of this needs testing and trying before you set off. Sit in the car and check and adjust the mirrors so that you have the best view possible. Have someone walk slowly round the vehicle so that you can get used to what is visible and what still isn’t. You will need to note the blind spots and keep them in mind as you drive.