Sno-Chain Ramp from TireChain.com
I heard that these snow ramps were called snow blocks back in the 1970's.
Purchased from:
http://www.tirechain.com/Sno-Chain-Ramps.htm
Wranglerstar demonstrates how to make your own snow ramps:
https://www.youtube.com/watch?v=bshkyfZDOGI