Standing Calf Raise

Trains the Gastrocnemius.

How to do it

Set the shoulder pads so that with the balls of your feet on the platform and your heels hanging off, you can stand up with your knees straight and a slight stretch in your calves.
Position the balls of your feet on the edge of the platform with your heels unsupported, feet about hip-width apart and pointing forward.
Stand up to take the weight, straighten your knees, and keep them straight for the whole set. This is what makes it a gastrocnemius exercise — bending the knee hands the work to the soleus underneath.
Lower your heels as far below the platform as they will comfortably go, until you feel a stretch through the back of the lower leg.
Push up onto your toes as high as you can and pause for a moment at the top.
Lower under control to a full stretch again. Pausing briefly at the bottom removes the tendon's bounce and makes the muscle start each repetition from a dead stop.

Bouncing through a short range. The calf's range of motion is short to begin with, so cutting it in half leaves almost nothing, and the Achilles tendon's elasticity does much of what remains. A full stretch at the bottom and a genuine pause is worth far more than added weight.
Bending the knees. A bent knee shortens the gastrocnemius at its upper end and shifts the work to the soleus — which is a legitimate exercise, but it is the seated calf raise, and doing it by accident means the standing version trained something other than what was intended.
Neglecting the seated version entirely. The soleus is the larger of the two calf muscles and it only gets loaded properly with the knee bent. A calf routine of standing raises alone has left the bigger muscle undertrained.
Rushing the repetitions. The calves are loaded by walking all day, so the training stimulus has to exceed a high baseline. Slow, full, paused repetitions do that; fast partial ones do not.