What is a rocker plate? These rocker plate things always looked like a gimmick to me, but after doing more research it turns out that they make riding on an indoor bike trainer way more comfortable. Something about the bike rocking side to side and sliding back and forth helps you move around on the bike seat more. Helps your butt move around instead of just staying on the same pressure points. I decided to make my own, and after using it, I can confirm it makes a big difference. I can now start doing longer 2-3 hour rides inside during the cold winter here in Mass. I can also confirm that adding the rubber feet to the bottom helps cut down on the noise, Jacqui doesn't even hear me at all now when I'm pedaling up in the attic above her bedroom. Parts I used for this build ($250-300 total usd I think) a 3/4" and 4'x8' sheet of baltic birch plywood or equivalent from a speciality plywood supplier. My local HomeDepot doesn't carry baltic birch playwood ...