The modern garbage disposal has been a tremendous boon for homeowners and renters worldwide. It provides a quick and sanitary way to dispose of food waste, keeping trash bags lighter and landfills from overflowing. Because of their simplicity and solid construction, disposals are workhorses, potentially grinding away year after year. But even this venerable appliance can choke on certain items. Here are 15 things to never put in your disposal if you want to keep it running smooth and your drains clog-free.