The tension rods are used to secure your glory hole in place. An additional rod can be useful for some configuration options. Having a visitor seated on a chair, a third tension rod keeps things nice and neat. Of setting up in a hallway a third tension rod allow you to create a "box" set up.  Also great for anonymous spanking set ups. Use overtime can also lock the spring mechanism and stop them adjusting so if you’re planning to put the miles in with your gloryhole having an extra rod on standby is worth thinking about.