You will need an open door and your resistance bands for this exercise. 

Resistance Band Setup

Loop your resistance band over the top of the door so there is an even length on either side of the door

Resting Position

Grab the middle of the resistance band to create a 45° angle, keeping your elbows by your side. 

Action

Keeping your elbows by your side, pull the resistance band down. Come back to resting