Mark drill hole guides on scrap piece of wood spacing them 1-inch apart.
Drill holes in base of one bin using 1/4-inch drill bit. To avoid cracking bin, press bottom of bin against wood below as you drill or use a step-down drill bit.
Stack bin with holes on top of the second bin.
Add a few inches of pine pellets.
Remove solid waste with scoop. Push sawdust through holes to bottom bin and clean out as needed.
Be sure to use bins with side handles which create a gap between bins when stacked allowing room for wet pellets (sawdust) to fall. To make your cat litter system more eco-friendly, consider using a pet waste compost bin if you have room outdoors and switch to truly biodegradable bags if discarding waste in garbage system. For the best deal on wood pellets, check for wood stove pellets or horse stall pellets and check that there are no added ingredients.