I have been using three guages of kitchen strainers to seperate small arthropods from the bulk of the litter in which they reside but I decided to speed the process up by removing the coarser litter first with these modified plastic bins.

I removed the bottoms of two bins using first a small power saw to start my cut, then using a hand-held jigsaw to complete the cuts. I then snipped and bent two guages of hardware cloth (galvanised welded wire mesh) to fashion sieve bottoms for these bins. Finally I glued them in place by drizzling clear Gorrila Glue in the corners. The glue expands into a tough foam, trapping the wire mesh.