A penetrative position, where both get to sit down on the job, that can make for a difficult entry, and in keeping the penis in, during the penetration action.
Getting into position, and effecting entry can be difficult in this position. (fairly simple for those heterosexual types, but a bit of effort, and two guys can manage.)
The Giver (the one doing the penetrating) sits down on a flat surface, such as a good bed.
Facing the Giver, the Receiver (the one being penetrated) also sits down, with their legs on the outside of the lower body of the Giver.
Here comes the tricky part.
Spreading their legs apart, the Giver then helps the Receiver lift their legs upwards onto the Giver's shoulders.
At the same time, move the Receiver's body in closer, and have them lift their lower body upwards a little.
This will allow for entry to the rectal area.
Course, if you are a Lesbian couple, well, you can use either hole, right?
You may need to guide the penis to the hole, and with your hands holding onto the hips, you can pull your partner inwards, to help with the initial entry.
Once you have achieved penetration, you would use your hip action to generate the thrusting motion, so orgasm can be reached.
Once entry has been achieved, and while thrusting, this position does allow the Giver to help please their partner, as the penis would be exposed, for easy reach and fondling.
Adjusting how the Receiver's legs are spread, can aid in reaching penetration.
It can also help in how the penetrating thrusts are maintained.
The Receiver can also help in this area, by their own hip action.