Grover,
As you can see and read, many folks have different ideas on what to use and whether or not to make them or buy them. It's all a matter of opinion. As long as they're stable, strong, non-slip type blocks, anything will work. I carry a small lumber yard with me. I've got (4) 4x10x20 that are beveled at one end. Those are primarily for the rig to drive on in the rear if, the rear is low when we enter a campsite that may need that kind of augmentation.
I also carry some 2"x10"x20" that are sandwiched between two 5/8" Birch plywood for additional leveling (primarily for the front wheels). And finally I carry (4) 11"x9" solid lumber, also sandwiched between the same Birch plywood for the jacks. Yep, it takes up a bit of room but, it's there for a purpose and, almost all of it is used on a fairly regular basis. I'm one of those types that does the "primary leveling" with the tires and wheels and use the jacks for "fine tuning" type thing.
That little lumber yard has come in handy way more times than you'd think. I've installed "eye bolts/screws" on all of them so a little bent arm can retrieve them when it comes time to pack up and move on to another sight. Way easy that way.
Scott

