The job of the rubber shield at the top of the disposal is to keep fast-moving food particles from being ejected out of the disposal. The stopper lets you plug the sink to hold water when you're not using the disposal

For the most part, garbage disposals are self-cleaning and virtually maintenance free. However, a malfunctioning garbage disposal can mean a messy headache, but one that can be avoided. Here are some ideas to keep your unit in good working order.

Always run cold water when grinding in order to move the waste all the way through the drain lines. Fats and grease congeal and harden in cold water which can then be flushed through the system. Don't use hot water when grinding because it can dissolve fats and grease, which may then accumulate in the drain line. Almost all biodegradable food waste can be fed into disposals. However, do not throw down the disposal clam or oyster shells, corn husks or other material with a high fiber content. Under no circumstances should you put glass, plastic or metal non-food materials through a disposal. This includes bottle caps, tin covers or aluminum foil--these are some of the items service technicians commonly find in clogged or broken disposals.

Maintenance is easy. Grinding small bones and egg shells actually helps clean the disposal by scraping away stubborn deposits or citric acid and pulp. Grinding a little ice is another way to clean out deposits and get rid of odors.