In years past I used the
2x6 wood planks like others but they were heavy and awkward to store,I then tried the Lego type blocks but found that they broke to easy and were a pain to setup when you don't get it right the first time and had to drive off,re-stack, and make them higher,to labor intensive.
When I bought my RV,a former Rental, it came with
Tri Level Ramps They don't break and if they are good enough to withstand the use in that market they must be good.
I have used them a lot and have had no problems and they are easy to use and store. 4 is the most I have ever needed,most times just 2 if at all.