I took (4) 2' long pieces of 2"X8". One cut on each piece at 45 degree angle. Lay one on top of the other with about 6"-8" overlap. Use sheetrock screws to fasten the two pieces together. You'll end up with ramps with angled leading edges that will ultimately raise the car about 3.5" with sort landings that prevent the ramps from skidding. I use them alone to raise the car for draining coolant or
oil, or so I can get my cheapie Harbor Freight jack under the low hung front crossbar if I want to raise it further for jack stands. Recessed holes can also be drilled to allow for a bolt to be inserted into the concrete to prevent them from sliding (not really required). Not the best solution but for about $15.00 it works.