This is my jack:
If you look closely, you can see two 3/4" holes in each rubber piece.
I am lifting under a 1.5 qt. sump. Because of concern that the sump will slip off the rubber pieces, I put a piece of 3/4" plywood on top. I used tee-nuts to fasten 3/4" spacers on the bottom to fit into the holes in the rubber.