Bad posture exercises need a wall

Aging causes poor posture--at least that's my excuse. I have to really think to sit or walk with good posture. When I look at Silver Sneakers' instructions to correct this, they always suggest doing something with a wall. I have doors, windows, rooms with chair rails, wide openings, banisters, furniture either floating or against the wall and maybe 50 paintings, but no wall space for doing chin tucks, corridor stretches, hands against the wall, etc.

https://www.youtube.com/watch?v=WJspJaFL_l8   This is not Silver Sneakers, but the moves aren't difficult and some are sitting or standing (without the help of a wall).