Set-up: Start by standing with your back against a wall with proper upright posture. Raise your upper arms out to your sides and your forearms to vertical.
Movement: Pressing the forearms against the wall, and keeping them in contact throughout the movement, slide them up until your arms reach full extension. Slide your arms back down, focusing on pulling your shoulder blades together and down. Bring your elbows into your body and squeeze your shoulder blades together at the bottom of the movement.