The two most common variations of the triceps pressdown involve doing them with a rope or an attachment like a V-bar or straight bar. The rope variation places more constant tension on the triceps by isolating them while the metal bars allow greater overload. Each provides its own unique hypertrophy stimulus. But it's possible to take advantage of each of the stimuli by combining both methods.
Negative Accentuated Rope Pressdowns
Using a heavy weight, tightly press both ends of the rope together and push the weight down. Because both arms will be assisting each other and pressed together rather than separately, you can get maximal overload like you would using a bar.
Once you reach the bottom of the movement, deliberately spread the handles as much as possible and hold this position several seconds before doing a slow 5-second negative.
Because you'll be using both arms on the concentric phase, the slow negative can be done with significantly greater weight than what could typically be handled for traditional rope pressdowns.
This maximizes all three major mechanisms of muscle hypertrophy including micro trauma (muscle damage), intramuscular/mechanical tension, and cellular volumization (muscle pump). The burn can be intense, but if you're able to tolerate the pain you'll be rewarded with growth.
Due to the extended time under tension, use moderate rep ranges of 6-10 reps. However, you can also use this as a triceps finisher by doing a single set 12-20 reps at the end of your workout.