A sign rider is the smaller sign that hangs from or attaches to the main for-sale yard sign, used for details like "Open Sunday" or an agent phone number. It is high-visibility real estate that every passerby already looks at.
It is also the best place to put an open house QR code. A visitor can scan it from the curb and sign in on their own phone before they even walk in, which starts lead capture earlier and clears the line at the door.