Yep, For holding twigs and straw in finch cages. You can't lay the nesting mateials on the floor of the cage because they get fouled with poop and the birds won't use them.
Hey Doug, My aunt filled hers (made of glass and plastic) with seed she called treats when they weren't being used for nesting materials. The birds only nest once or twice a year and the rest of the time it was treats time.[] She also hung some strange broom stuff from the top of the cages that the birds nibbled at and then would use for nesting. Don't know what it was though.