Leveling chocks

I also use Andersen leveler on my 30 travel trailer. But SoundGuy is correct as far as them sinking in soft earth, but then again, so will any blocks to an extent. Another issue that SoundGuy mentions is that they can slip out from under the wheels under certain conditions when backing or driving onto the levelers. I have just ordered some self-adhesive rubber safety matsto attach to the Anderson levelers and hope that will solve the issue of slippage.