One version with a step (probably more aggressive and/or effective), and below a version to use if you don't have a step, that can be just as effective. Choose the one you prefer or the one that feels right. Do get in touch should you wish to discuss which one is most appropriate for yourself. The stretch should be felt in the upper calf with the knee straight, and in the lower calf with the knee bent. If the stretch is felt in the Achille's tendon, you might have an inflammation or pathology at that level and stretching it might not be the best idea, as it might increase the irritation locally. Do get in touch if in doubt. Likewise the stretch shouldn't be felt at the front of the ankle, as this may indicate an ankle mobility problem (which in itself may maintain the calf tightness and probably needs addressing before going on with the stretching). As always, get in touch if you have any questions, and use these stretches at your own risk.