Make ramps safe and rabbit friendly by covering with carpet or a mat. Or add bits of wood to create a step effect and allow your rabbit to have more grip on the ramp. Never position a ramp too steep
A majority of dog crates are not big enough on their own for house rabbits, so you will need to have a run also attached as the dog crates are only usually 4ft in length. Some dog crates can be difficult to clean out.