I sometimes used a 4X4 block about 10" - 12" wide on top of the jack especially for my vehicles that sit up a little higher. I've never had a problem with the block slipping out. Sometimes it makes creaking type of noises but I've never had any problem. Of course I NEVER get under the vehicle unless it is supported by jack stands.
And I'll agree with all the others - I learned the hard way to never use any type of cement block when jacking a car. I tried it once when I was rather young and you can all guess what happened! Fortunately the only harm done was to my nerves!
And I'll agree with all the others - I learned the hard way to never use any type of cement block when jacking a car. I tried it once when I was rather young and you can all guess what happened! Fortunately the only harm done was to my nerves!