If you replace the shelves with wood (untreated pine only) or wire (1/4" x 1/4" mesh wire), that would be much more acceptable than the plastic shelves.
To replace the plastic shelves with wood ... go to your local lumber yard or hardware store and have them cut you pieces to fit where the shelves will sit. You can take the measurements yourself or, even better, take the plastic shelves out and take them to the store with you to assure you are getting the correct size. Most places will cut the shelves to size for you (for a minimal charge per cut).
To attach the shelves to the cage, you will need wood screws and fender washers. (Enough screws for at least 2 screws at both ends of the shelf/shelves and 2 to 4 screws along the side of the shelf that touches the wire on the side of the cage.)
You will need a drill bit (to pre-drill holes) smaller than the screw and a screw driver to put the screws into the wood.
The fender washers have to be big enough to cover at least 2 or 3 wires on the side of the cage, with the centers of the fender washers smaller than the head of the wood screws you will be using.
It is best to pre-drill small holes into the sides of the wood to keep it from splitting when putting in the screws.
When ready to attach your new shelves, place the new wood shelf inside the cage where it will be set, then, place a fender washer over the pre-drilled hole on the wood inside the cage, then place a second fender washer on the outside of the cage, line them up and screw in the screw. (easier done with 2 people) This should hold the shelf in place. Each shelf will need at least
two screws for each end and depending on the size and 2 to 4 screws for the long side of the shelf in the cage.
***Remember, you need
2 finder washers for each screw you use to put up each shelf and/or leaping ledge ... make sure you use fender washers that have a center hole smaller than the head of the wood screws or they will be of no use.
Leaping ledges are expensive when bought as a 'leaping ledge', it is much more economical to make your own by using cuts of wood and attach them the same way as the shelves above.
Corner leaping ledges can be made by cutting a square piece of wood diagonally making two triangle shapes out of it. These can be placed in the inside corners of the cage ... use 4 screws per corner ledge (two screws for each side of the ledge touching the cage wire).
While you are at the store ... pick up some sand paper to help keep the wood shelves clean and smooth. The chins will 'decorate' the shelves by gnawing away at them.
Hope this helps!
Jo Ann