There are all kinds of things you can do for ramps.
bend a grid and carpet it
use pencil boxes
use bricks (my gang will jump on top of a pigloo and then up on the second deck. In one of my cages, I don't even have a ramp, they just jump up there)
If you look in the photo section, you will find all kinds of nifty ideas for ramps.
I just use a piece of folded coroplast for my ramp. I attached it at the top level using 2 zip ties. I also attached a piece of towel down the center for "footing". When I clean the cage I just flip it up to the second floor. It works well.