This is a great exercise that targets triceps while requiring only dumbbells
Grab a dumbbell using both your hands with appropriate weight.
While keeping your body upright, bring the dumbbell straight above your shoulder until your arms are fully extended.
Slowly bring the dumbbell down till your upper arm and forearm are perpendicular to each other, isolating the triceps during this movement.
After a pause, slowly bring the weights back up to the start position.
Once completing your set, re-rack the equipment as needed.
Start with low weights as this is an isolation movement that requires a lot of control.
Modifications include using a pulley machine with bar extension or a barbell while keeping your grip close to shoulder width apart.