Best way to keep REL sub from “hopping around” at high volumes

Hey folks, any “best practices” for keeping my REL sub in one place at high volumes?  It’s on hardwood (and/or tile), no carpet.  Besides using something sticky on the feet — like double sided tape, I can’t think of anything besides a brick on top, lol.    Anything that’s worked for you ?   Of course, only happens at high volumes, it tends to vibrate itself around a bit (nothing crazy),   Ideas?

 Thanks, Jim