The blocks should at least be oriented with the holes running vertically...

https://askinglot.com/which-way-is-a-cinder-block-strongest

. . . and a piece of three-quarter plywood on top for good measure.

_{(no, I've never done that. Really.)}

Ageeing with Rixter Concret blocks are quite strong vertically but quite weak in the position shown and will easily break. literal death trap pictured! 2X6 or 2 X8 wood on top of the blocks is also an excellent suggestion; makes sure forces are transmitted to the end and sides of the vertical oriented blocks. Only thing worse would be to stand them on end with the 8x8 down and 16 up. That is the weakest orientation.

Well if you've never woken up one morning to find your car on blocks and the wheels missing....you've lived a charmed life...everybody used blocks in the old days, I don't remember any jack stands...

Ummm, I used to use wooden blocks of fire wood, before I split them. 6x6 about 2 feet long stacked in a crib also works.

Closest mishap I had was as a 15 year old teenager using a jack-all under the rear bumper to change a flat on a car (late 60's) the jack tipped sideways when the wheel was off - hell of a job to get a jack under the vehicle sitting on the ground without wheels. Always blocked the vehicle after that.

And then there are the roadside flat changes and all that happens is the jack supplied with the car just sinks into the soft shoulder gravel.

This guy is just an idiot. Never learns from the first mishap. Should get a Darwin award.

A friend of mine was checking the front wheel bearings on his pickup,and had the tire up about 2 inches off of the ground.He was only going to check for end-play.When he put his hand under the tire,the jack slipped,pinning his hand to the ground.He tried pulling,digging and screaming,but his son was mowing grass in the back yard and could not hear him.His throat eventually went dry,and even though he was screaming,no sound was coming out,just a weak croak.

So there he was,hand pinned to the ground until his son finished mowing the grass and came around the house.

No bones were broken,but the tire tread pattern was pressed across his fingers as a purple bruise,like a tattoo.

He said the would have tried to call 911 with his toes on the cellphone,but he couldn't get his shoes off.

It has been many years ago,but he said the he could draw that pattern from memory even 50 years later.

A friend of mine was checking the front wheel bearings on his pickup,and had the tire up about 2 inches off of the ground.He was only going to check for end-play.When he put his hand under the tire,the jack slipped,pinning his hand to the ground.He tried pulling,digging and screaming,but his son was mowing grass in the back yard and could not hear him.His throat eventually went dry,and even though he was screaming,no sound was coming out,just a weak croak.

So there he was,hand pinned to the ground until his son finished mowing the grass and came around the house.

No bones were broken,but the tire tread pattern was pressed across his fingers as a purple bruise,like a tattoo.

He said the would have tried to call 911 with his toes on the cellphone,but he couldn't get his shoes off.

It has been many years ago,but he said the he could draw that pattern from memory even 50 years later.

I carry a piece of 2x12 pine and a small floor jack in my car just in case.The 2x212 make a stable base for the jack.Some say that is overkill,but what price otherwise?

Makes great firewood in a pinch too!