The T-bar row is one of the most popular back exercises out there for a good reason. It works.
The old school T-Bar row
All you need is a barbell, neutral grip handles, weights and a corner.
You can also use small plates in order to increase the range of motion.
Note: This picture demonstrates increased range of motion which is possible thanks to smaller plates.
One arm T-Bar row
You can also do the exercises with one arm if you want to focus more one side of the body and develop unilateral strength.
Chest Supported T-bar row
Another option which is easier on the lower back is the chest supported T-Bar row. This varitiation requires a machine and does not strengthten the lower back quite as much.
Machine T-bar row
Is some gyms you can find a special machine for T-Bar rows. The main benefit over an old school T-Bar row is that it's faster to set-up and does not damage the property of the gym.
FAQ:
Q: Do you think the T-Bar row is good exercise for back thickness?
A: If by back thickness you mean bigger upper back then yes.
Q: Can I use T-Bar rows instead of deadlifts?
A: Yes, but make sure you don't do chest supported rows in order to make the lower back stronger.
Q: How many sets and reps do you recommend?
A: It depends on your whole program.