Rope Triceps Pushdown

Trains the Lateral Head and Medial Head.

How to do it

Attach a rope to a high cable pulley and stand facing it, about a foot back.
Take one end of the rope in each hand with your palms facing each other.
Pull the rope down until your upper arms are against your sides and your elbows are bent to about ninety degrees.
Keeping the upper arms pinned, straighten your elbows and push the rope down.
At the bottom, pull the two ends of the rope apart and slightly back, so your palms end up facing the floor. This extra spread is what the rope offers over a bar.
Let the rope rise back under control until your forearms are just past parallel to the floor.

Not separating the rope at the bottom. Holding the ends together for the whole movement makes it a bar pushdown with a rope attached — the spread at the end is the point.
Letting the elbows travel forward and back. The upper arms should be still; once they move, the lats and shoulders start pressing the weight down.
Leaning over the rope to use bodyweight. Stand tall or take a small split stance.
Doing only pushdowns. With the elbows at the sides the long head is shortened at the shoulder and contributes little, and it is the largest of the three heads.