Arch Sex Position
To do the Arch position, the receiver gets into a partial bridge position with their shoulders resting on the bed while their partner enters from a kneeling position. The Arch is often overlooked because of its perceived simplicity, but thanks to the fantastic penetration angle this sex position offers, it should be a regular part of everyone's routine. That being said, you'll want to make sure to use a pillow under the receiver's head to reduce the strain and risk of injury to their neck.
Bridge Sex Position
A kneeling position for the man, the bridge gives you a wonderful view of her breasts and torso while demanding a lot of her physically. While she creates an arch with her arms and legs, you kneel in front of her and penetrate her. She won't be able to do too much moving, aside from keeping herself upright, so your job is to grab her ass and start pulling her hips back and forth to get the necessary motion to make the whole thing work. Supporting her ass with your hands a bit will also take some of the strain off her arms. The Bridge position is similar to the Arch, but with the receiver's arms behind/below them to hold their upper body off the bed or couch, while their partner enters from a kneeling position. The Bridge is often overlooked because of its additional difficulty.