Chair

An erect penis... When a guy is hanging out with a girl and she leaves the room for a minute, he pull his dick out and get it hard so when she comes back he can offer her a "chair"

She might say "aww thanks babe, so thoughtful! you pulled up a chair for me, now I have somewhere to sit"

Or if she doesn't notice right away he might say "I pulled up a chair for you, have a seat. You're welcome"